Gem upgrades

This updates several gems to their latest versions, include Active* and Rspec.  Several deprecated rspec features were replaced with their recommended counterparts.

Verification Steps:

- [x] Travis passed this build, no exceptions.
- [x] `rake spec` passes locally
- [x] VERIFY: No core code changes.  All changes are within the `spec` directory or the Gemfiles.
- [x] Start `msfconsole`.  VERIFY: No errors.
- [x] Use msfconsole for a few minutes.  Run a scan, run an exploit, use `irb`, etc.
- [x] VERIFY: No unexpected errors.

I realize these aren't the best verification steps. If you have any suggestions for better ways to verify, please let me know.