Fix Java regex syntax for disallowed characters

The dash character needs to be escaped so that it is not treated as regular expression syntax for a range of characters between the colon and underscore (':-_').
Merge branch 'patch-1' of git://github.com/mjr5749/librato-java into mjr5749-patch-1
Add basic sanitizer tests
Merge branch 'mjr5749-patch-1'