metasploit-version install

`metasploit-version` is a command line tool provided by the `metasploit-version` gem for running various commands that help with setting up and maintaining semantic versioning that is conforming to the `metasploit-version` gem's expectation.  `metasploit-version install` does the following:

1. Add the `metasploit-version` gem as a development dependency to the current project.
2. Generates a conforming `version.rb`
3. `bundle install` any dependencies for `metasploit-version`
4. Generates `CHANGELOG.md`
5. Generates `CONTRIBUTING.md`
6. Generates `RELEASING.md`
7. Generates `UPGRADING.md`
8. Sets up rspec, including automatically using the shared examples from the `metasploit-version` gem.

# Verification Steps

- [ ] `bundle install`

## Automation

### `rake spec`
- [ ] `rake spec`
- [ ] VERIFY no failures

### `rake cucumber`
- [ ] `rake cucumber`
- [ ] VERIFY no failures

### `rake yard`
- [ ] `rake yard`
- [ ] VERIFY no warnings
- [ ] VERIFY no undocumented objects

## Manual

- [ ] `gem build metasploit-version.gemspec`
- [ ] `cd /tmp`
- [ ] `rvm use @metasploit-versioned`
- [ ] `bundle gem metasploit-versioned`
- [ ] `gem install $OLDPWD/metasploit-version.gem`
- [ ] `metasploit-version install`
- [ ] VERIFY you are prompted for conflicts with files produced by `bundle gem`
- [ ] Answer `y` to take `metasploit-version install's version for each file with conflicts
- [ ] VERIFY bundle install is run by `metasploit-version install`
- [ ] VERIFY all files outlined in the above description are generated and that there are no typos or other errors in the files.