Add --format option with support for "text" and "compact" as per csslint.

Adds the `--format` and `--noSummary` options:

`--format` defaults to "text", aka the existing format for lint errors. It may also be set to "compact", which uses "file:line:error" one-line-per-error style which can be easily integrated into many IDEs to highlight errors while editing.

`--noSummary` avoids outputting the summary block of text for each file, and is automatically set by `--format=compact`.

This pull request includes the line-number changes in my other pull request, twitter/recess#39.