process.stdout.write and process.stderr.write

__tl;dr:__ I realize you want to keep this module small. Feel free to reject this PR; in which case I'll maintain my own shim.

This PR adds `write` methods to `process.stdout` / `process.stderr` which simulate the corresponding methods in Node.

The new `write` methods:

0. Simulate printing without a new line
0. Can handle control chars (`‘\r’`, `‘\b’`, `‘\n’`)
0. Use `console.log` / `console.error` as proxies for `stdout.write` / `stderr.write`

__Example:__

```Javascript
process.stdout.write("hello");
process.stdout.write("world\n");
process.stdout.write("foo");
process.stdout.write("\rbar\bz\n");
```

Will print (exactly as in Node):

```
helloworld
baz
```

While doing the same with `console.log` will print:

```
hello
world

foo
barz

```

__Note:__

Prints are buffered until a `'\n'` char is encountered. So `process.stdout.write('foo')` will print nothing.