Adding _site to gitignore
Adds --require switch to allow user specific config

This will allow people to configure bundler, sass plugins, special
configurations, etc.

refs: #54
Deprecates --compass-with-config

I knew that was a bad decision. --require will be a lot simpler

refs: #54
Parses and ignores @import statements

Users will need to run csscss on those specific files.

This also fixes a bug where comments were being merged with selectors.

refs: #41, #57, #58
Formatting the switches a little
Cleans up some require/abort lines
Adds an experimental flag to ignore sass mixin declarations

Users can now do this with --ignore-sass-mixins.

This is a heavily requested feature. Some users don't care about
duplication coming from sass mixins. So this will inject a special
comment before/after the properties from the mixin and the parser will
ignore it.

This will mess with reporting selector line numbers if I implement that
in the future.

I'm not sold on this being the default yet.

refs: #25, #59
Bumping version for 1.3.0 release
Updates README with --ignore-sass-mixins info
Merge branch 'master' into gh-pages
Merging README update