Corrects ERR trap

function fw_exists was returning a non-zero code, which was always
triggering the ERR trap. This commit fixes that issue for the "go"
dependency - it still needs to be fixed for others.

This also updates the ERR trap to have access to the entire
bash function stack, which would be very useful for debugging
Apply ERR fix to all dependency installer files

Minor bugs fixed:
- Ruby was triggering ERR trap
- Erlang was untarring nonexistent file
- Composer was being installed into nonexistent directory
- Mono was incorrectly trying to move it's install location
- Yesod now depends on haskell