Remove the extra trim from String.isBoolean

Save the extra trim.
Remove unnecessary null checks
Make the hex character set string finalized. 

Most JIT should catch this, but it should be find to write it like this.
Add semi-colon

Thanks Travis! xD
Darn, that is strict!

Removed trailing space.
Wrap with () to show immediate invocation.
Revert closure.
Merge pull request #535 from gravypod/patch-1

Remove unneeded code from src/lang/string.js (gravypod)