Simplify printing tab summary in `brew info`

This cleanups up some stuff in `brew info` by pushing into `Tab#to_s`. Rather than use two lines per keg, they are now combined:

From bottle:

```
/usr/local/Cellar/jpeg/8d (18 files, 780K)*
  Poured from bottle
```

From source with options:

```
/usr/local/Cellar/gettext/0.18.2 (372 files, 15M)
  Built from source with: --universal
```

From source with options, installed before the `poured_from_bottle` flag was added:

```
/usr/local/Cellar/git/1.8.2 (1299 files, 26M)*
  Installed with: --with-pcre, --with-blk-sha1
```