Remove hard dependency on Bolt's lib method.

trimString had an old reference to getStringLength, which has since moved to Bolt\Library, and is otherwise unused in Bolt.  Copied the functionality inline here as this doesn't have (and probably shouldn't have) a composer requirement of Bolt. (Circular dependencies, wheeee!)

Cheers!
Merge pull request #2 from jkazimir/patch-1

Remove hard dependency on Bolt's lib method.