Make wrapper more robust and concise

* The "--help" page was getting too long to include for every client-side error and would in many cases push the actual error message off the screen. This change shortens the error message, instructing the user to run 'razor --help' for more information.
* Some exceptions were displaying stack traces to the user. This now catches a more robust set of exceptions.

For https://tickets.puppetlabs.com/browse/RAZOR-125
Better JSON error reporting

The error message for invalid user-entered JSON was not very helpful. The new error message states that the parameter is invalid.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-125