Convert non defined upper case constants to lower case.

fixes #88

Conflicts:
	src/main/java/com/google/gwt/resources/converter/Css2Gss.java
	src/test/java/com/google/gwt/resources/converter/Css2GssTest.java
Merge pull request #101 from dankurka/upper_case

Convert non defined upper case constants to lower case.