Update torquebox exec command

Updated the bundle_exec variable on line 208 to match the method_option name in line 202.

Updated :no_bundle alias to take a single letter following [Thor convention](https://github.com/erikhuda/thor/wiki/Method-Options)
added error info for better explanation

Fixed/Added error info when you run jruby -S cap deploy production:

cap aborted!
undefined method `instance' for Capistrano::Configuration:Class
(See full trace by running task with --trace)
Merge pull request #171 from statonjr/patch-1

Update torquebox exec command
Merge pull request #172 from suryart/master

added error info for better explanation