Fix gemspec to use ~> properly
Fix interactions with `*_path` and `*_dir` configuration options

Allows the usage of `sass_dir` and `css_dir` as you would expect. For
jekyll-compass `sass_dir` is relative to the Jekyll root, `css_dir` is
relative to the output root.

Fixes #9
Symbolize Compass options that require it

Fixes #10
Recursively symbolize key names

Fixes issues with :sass_options
Bump to 0.4.0.pre for further dev