Make railites a hard dep

MSP-11359

# Verification Steps

## Cucumber
- [x] `rake features`
- [x] VERIFY no failures

## Specs
- [x] `rake spec`
- [x] VERIFY no failures

# Post-merge Steps

Perform these steps prior to pushing to master or the build will be broke on master.

## Version
- [ ] Edit `lib/metasploit/concern/version.rb`
- [ ] Remove `PRERELEASE` and its comment as `PRERELEASE` is not defined on master.

## Gem build
- [ ] gem build *.gemspec
- [ ] VERIFY the gem has no '.pre' version suffix.

## RSpec
- [ ] `rake spec`
- [ ] VERIFY version examples pass without failures

## Commit & Push
- [ ] `git commit -a`
- [ ] `git push origin master`

# Release

Complete these steps on DESTINATION

## `VERSION`

### Incompatible changes

`MAJOR` was already updated and `PATCH` reset as changing railties from a soft to a hard dependency is an incompatible change.

## MRI Ruby
- [ ] `rvm use ruby-1.9.3@metasploit-concern`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install`
- [ ] `rake release`