Watch files and recompile on changes

[simpleshadow]

Resolve #15.

Example:

ember-precompile *.handlebars -f templates.js -w

When watching, ember-precompile will now automatically watch any referenced files for changes and recompile the output upon any changes to reference files.

Pull request includes the following changes:

• Passing argument -w indicates to watch specified files for changes and re-compiles them.
• Added new node module dependency, colors, for better logging.
• Included details in README.
• Bumped version number.
• Added self as contributor.

[nettles-jarrod]

Hi @simpleshadow, thanks for the PR but we've already discussed this functionality before and decided its preferable to let other libraries handle this.