Re-enable pry command

The switch to bundler broke pry. This change, along with starting
msfconsole with a command like: `ruby -r pry ./msfconsole`, makes using
it possible again.

## Verification
### The bug
- [ ] gem install pry
- [ ] start msfconsole
- [ ] run `irb` command
- [ ] verify that `require 'pry'` fails
- [ ] exit msfconsole

### The fix
- [ ] start msfconsle with `ruby -r pry ./msfconsole`
- [ ] run `irb`
- [ ] run `framework.pry`
- [ ] verify working pry console