Added time styles to NSDate#string_with_style
Merge pull request #47 from widescape/nsdate_string_with_style_with_time_format

Added time styles to NSDate#string_with_style
added 'root' option to 'pop' method, and some tests for `UIViewController`.
changed all symbol constants to `attr`s instead of `attr_accessors`
added UIColor mixing methods (actually, `+` has been there, but undocumented) +, mix_with, and invert
Merge pull request #46 from GantMan/master

UILabel and `fit`
added symbol-based templates to NSDate, via string_with_format and NSDate::SugarCubeFormats
refactored UIColor#to_s to delegate to to_i and to_hex methods
don't rely on unholy