Add method to report the smaps for a given pid

inspects either `/proc/self/smaps` or `/proc/<pid>/smaps` and returns the parsed results

```js
meminfo.smaps(function (err, results) {
  console.log(results.totals);
});
```

Output is:

```js
  {
    "size": "576.98 mB",
    "rss": "7.23 mB",
    "pss": "6.46 mB",
    "shared_clean": "980 kB",
    "shared_dirty": "0 kB",
    "private_clean": "3.25 mB",
    "private_dirty": "3.02 mB",
    "referenced": "7.23 mB",
    "anonymous": "3.02 mB",
    "swap": "0 kB",
    "kernelpagesize": "252 kB",
    "mmupagesize": "252 kB",
    "locked": "0 kB"
  }
```

There are top level objects for totals, heap, stack, vdso, vsyscall. The rest fall under the name of the file mapped or `<unnamed>` here is the sample structure

```js
{
  "totals": {
    "size": "576.98 mB",
    "rss": "7.23 mB",
    "pss": "6.46 mB",
    "shared_clean": "980 kB",
    "shared_dirty": "0 kB",
    "private_clean": "3.25 mB",
    "private_dirty": "3.02 mB",
    "referenced": "7.23 mB",
    "anonymous": "3.02 mB",
    "swap": "0 kB",
    "kernelpagesize": "252 kB",
    "mmupagesize": "252 kB",
    "locked": "0 kB"
  },
  "heap": {
    "region": "01827000-018a5000",
    "permissions": "rw-p",
    "offset": "00000000",
    "device": "00:00",
    "inode": "0",
    "path": "[heap]",
    "size": "504kB",
    "rss": "500kB",
    "pss": "500kB",
    "shared_clean": "0kB",
    "shared_dirty": "0kB",
    "private_clean": "0kB",
    "private_dirty": "500kB",
    "referenced": "500kB",
    "anonymous": "500kB",
    "swap": "0kB",
    "kernelpagesize": "4kB",
    "mmupagesize": "4kB",
    "locked": "0kB"
  },
  "stack": {
    "region": "7fffb4204000-7fffb4225000",
    "permissions": "rw-p",
    "offset": "00000000",
    "device": "00:00",
    "inode": "0",
    "path": "[stack]",
    "size": "136kB",
    "rss": "32kB",
    "pss": "32kB",
    "shared_clean": "0kB",
    "shared_dirty": "0kB",
    "private_clean": "0kB",
    "private_dirty": "32kB",
    "referenced": "32kB",
    "anonymous": "32kB",
    "swap": "0kB",
    "kernelpagesize": "4kB",
    "mmupagesize": "4kB",
    "locked": "0kB"
  },
  "vdso": {
    "region": "7fffb436a000-7fffb436b000",
    "permissions": "r-xp",
    "offset": "00000000",
    "device": "00:00",
    "inode": "0",
    "path": "[vdso]",
    "size": "4kB",
    "rss": "4kB",
    "pss": "0kB",
    "shared_clean": "4kB",
    "shared_dirty": "0kB",
    "private_clean": "0kB",
    "private_dirty": "0kB",
    "referenced": "4kB",
    "anonymous": "0kB",
    "swap": "0kB",
    "kernelpagesize": "4kB",
    "mmupagesize": "4kB",
    "locked": "0kB"
  },
  "vsyscall": {
    "region": "ffffffffff600000-ffffffffff601000",
    "permissions": "r-xp",
    "offset": "00000000",
    "device": "00:00",
    "inode": "0",
    "path": "[vsyscall]",
    "size": "4kB",
    "rss": "0kB",
    "pss": "0kB",
    "shared_clean": "0kB",
    "shared_dirty": "0kB",
    "private_clean": "0kB",
    "private_dirty": "0kB",
    "referenced": "0kB",
    "anonymous": "0kB",
    "swap": "0kB",
    "kernelpagesize": "4kB",
    "mmupagesize": "4kB",
    "locked": "0kB"
  },
  "vsyscall": {
    "region": "ffffffffff600000-ffffffffff601000",
    "permissions": "r-xp",
    "offset": "00000000",
    "device": "00:00",
    "inode": "0",
    "path": "[vsyscall]",
    "size": "4kB",
    "rss": "0kB",
    "pss": "0kB",
    "shared_clean": "0kB",
    "shared_dirty": "0kB",
    "private_clean": "0kB",
    "private_dirty": "0kB",
    "referenced": "0kB",
    "anonymous": "0kB",
    "swap": "0kB",
    "kernelpagesize": "4kB",
    "mmupagesize": "4kB",
    "locked": "0kB"
  },
  "/home/tjfontaine/.give/installed/master/bin/node": [
    {
      "region": "00400000-00bff000",
      "permissions": "r-xp",
      "offset": "00000000",
      "device": "08:01",
      "inode": "556304",
      "path": "/home/tjfontaine/.give/installed/master/bin/node",
      "size": "8188kB",
      "rss": "3292kB",
      "pss": "3292kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "3292kB",
      "private_dirty": "0kB",
      "referenced": "3292kB",
      "anonymous": "0kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "00dfe000-00dff000",
      "permissions": "r--p",
      "offset": "007fe000",
      "device": "08:01",
      "inode": "556304",
      "path": "/home/tjfontaine/.give/installed/master/bin/node",
      "size": "4kB",
      "rss": "4kB",
      "pss": "4kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "4kB",
      "referenced": "4kB",
      "anonymous": "4kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "00dff000-00e10000",
      "permissions": "rw-p",
      "offset": "007ff000",
      "device": "08:01",
      "inode": "556304",
      "path": "/home/tjfontaine/.give/installed/master/bin/node",
      "size": "68kB",
      "rss": "16kB",
      "pss": "16kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "8kB",
      "private_dirty": "8kB",
      "referenced": "16kB",
      "anonymous": "8kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    }
  ],
  "<unnamed>": [
    {
      "region": "00e10000-00e1a000",
      "permissions": "rw-p",
      "offset": "00000000",
      "device": "00:00",
      "inode": "0",
      "path": "<unnamed>",
      "size": "40kB",
      "rss": "28kB",
      "pss": "28kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "28kB",
      "referenced": "28kB",
      "anonymous": "28kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "badfc2b000-badfc40000",
      "permissions": "---p",
      "offset": "00000000",
      "device": "00:00",
      "inode": "0",
      "path": "<unnamed>",
      "size": "84kB",
      "rss": "0kB",
      "pss": "0kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "0kB",
      "referenced": "0kB",
      "anonymous": "0kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "badfc40000-badfc60000",
      "permissions": "rw-p",
      "offset": "00000000",
      "device": "00:00",
      "inode": "0",
      "path": "<unnamed>",
      "size": "128kB",
      "rss": "24kB",
      "pss": "24kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "24kB",
      "referenced": "24kB",
      "anonymous": "24kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "badfc60000-badfc8b000",
      "permissions": "---p",
      "offset": "00000000",
      "device": "00:00",
      "inode": "0",
      "path": "<unnamed>",
      "size": "172kB",
      "rss": "0kB",
      "pss": "0kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "0kB",
      "referenced": "0kB",
      "anonymous": "0kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "8dc33500000-8dc33600000",
      "permissions": "rw-p",
      "offset": "00000000",
      "device": "00:00",
      "inode": "0",
      "path": "<unnamed>",
      "size": "1024kB",
      "rss": "84kB",
      "pss": "84kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "84kB",
      "referenced": "84kB",
      "anonymous": "84kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    },
    {
      "region": "12d6dc000000-12d6dcf00000",
      "permissions": "---p",
      "offset": "00000000",
      "device": "00:00",
      "inode": "0",
      "path": "<unnamed>",
      "size": "15360kB",
      "rss": "0kB",
      "pss": "0kB",
      "shared_clean": "0kB",
      "shared_dirty": "0kB",
      "private_clean": "0kB",
      "private_dirty": "0kB",
      "referenced": "0kB",
      "anonymous": "0kB",
      "swap": "0kB",
      "kernelpagesize": "4kB",
      "mmupagesize": "4kB",
      "locked": "0kB"
    }
  ]
}
```