Added Configuration - Seperating out duration from style 

Style is too limiting and the wrong name now. It contains aspects which should be available to none styled croutons.

Configuration file is dependant to Style/CustomView meaning we can set a duration on the Custom views!! Yay!

Please note, Only look at the last commit. I can cherry pick for you if you would like?

This now allows Crouton.make(Activity,View,ViewGroup, Config)
Or Crouton.make(Activity,View,ViewGroup).setConfiguration(Config.Builder().build()).show()

And of course added to showText Method so users can define non default config.

Feel free to ask questions. Or implement the concept slightly differently.

**Commit as follows**:
Separated out the Non Visual config from Style, Configuration is dependant of how the crouton is displayed.

Issue being the duration (and potentially other items) should not be tied to the Visual aspect.

Cherry Picked from upstream & master and merged.