Merge pull request #222 from ripple/log-exceptions

[FIX] check for error/response prior to callback
[FIX] check for error/response prior to callback
[FIX] check if error is a string before error.match
[FIX] consolidate RippleRest error checking
t rebase master
Merge branch 'develop' of github.com:ripple/gatewayd into develop
[FEATURE] log uncaughtException