Bump to p547 to fix a regression in p545

In my excitement of landing #3281 I didn't check to see if there was a newer Ruby available. Turns out, p547 was released on May 16, and fixes a regression regarding OpenSSL.

Announcement:

https://www.ruby-lang.org/en/news/2014/05/16/ruby-1-9-3-p547-released/

Sorry about the shuffle.

## Verification Steps

- [ ] Merge this PR or check out this feature branch.
- [ ] `pushd .. popd`
- [ ] See the warning about the missing Ruby (if you don't already have it)
- [ ] `rvm install ruby-1.9.3-p547`
- [ ] `bundle install`
- [ ] 'pushd .. ; popd`
- [ ] See that Ruby is the correct patchlevel: `ruby -e "puts RUBY_PATCHLEVEL"`
- [ ] See that msfconsole is basically functional: `msfconsole -L -x "exit"`
- [ ] See that the specs all pass.