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

- [x] Merge this PR or check out this feature branch.
- [x] `pushd .. ; popd`
- [x] See the warning about the missing Ruby (if you don't already have it)
- [x] `rvm install ruby-1.9.3-p547`
- [x] `pushd .. ; popd`
- [x] See that Ruby is the correct patchlevel: `ruby -e "puts RUBY_PATCHLEVEL"`
- [x] `bundle install` to get freshly compiled gems
- [x] See that msfconsole is basically functional: `msfconsole -L -x "exit"`
- [x] See that the specs all pass.