Name change for ruby lib.

[tiegz]

I'd like to propose changing the Ruby lib name from ThreatExchange to threat_exchange everywhere.

Snakecase is the most common convention in Ruby (e.g. list of gems on Rubygems).

It's mostly a cosmetic change, but could help adoption of the library.

[wxsBSD]

This seems fine, but it may break existing scripts which use it. Do you have any sense for how many people this may break? I'm certainly not opposed to it but want to attempt to minimize breakage.

[tiegz]

@wxsBSD the Ruby lib was a little stale until last week, so I bet it won't be too bad. We may even be able to keep an alias around for a bit. I'll try it out later and might PR this.

[wxsBSD]

Awesome. I'll be closing this out and await a PR. :)