Update the way judging gravity

Support multi gravity values(separated by '|').
This way I can align the text with Gravity.CENTER_VERTICAL | Gravity.RIGHT or sth. else
add setTextColorValue to Style
reverts back to java 1.6
Merge branch 'set_text_color' of https://github.com/AngelDevil/Crouton into AngelDevil-text_gravity
replaces magic numbers with Style.NOT_SET
Merge branch 'text_gravity' of https://github.com/AngelDevil/Crouton into AngelDevil-text_gravity
updates copyright
gradle wrapper 1.10 and build tools 0.8+
java compatibility back to 1.6 for demo
version bump to 1.8.3