added overloaded join method for a Iterable
Reverse method
Added a null check for the separator
Added tests for reverse and join iterable
Added indexOfDifferences and its test
Doc for indexOfDifference
Merge pull request #18 from vjames19/MoreStringUtils

More StringHelper!
fix issue #19: NetHelperTest failes
add license to ScrollableTableTest
fix issue #20: a/b File left after running tests