Provide more informative exceptions. (Issue #204).

*   Better exception handling. (Issue #204)
    -   Hyde now propagates exceptions
    -   Hyde does not raise exceptions by default. `-x` flag is required
        for raising exceptions on error.
    -   Traceback is available in the `verbose` mode
*   Upgraded to commando 0.3.4
*   Upgraded to Jinja 2.7