To get the charlock_holmes gem working you need to pass a number of flags using bundle config.
Run the following from the command line within the project folder:
$ bundle config --local build.charlock_holmes --with-ldflags='-L. -Wl,-O1 -Wl,--as-needed -rdynamic -Wl,-export-dynamic -Wl,--no-undefined -lz -licuuc'
Commit the newly created file (/.bundle/config) to version control and redeploy.
This solution based largly on advice I received from Engine Yard support who also referenced from within the projects github issues. https://github.com/brianmario/charlock_holmes/issues/32#issuecomment-17033186