upgrade runtime dependencies

[mycargus]

Relying on TravisCI to run the tests here. I tried running them but all I got was this error:

Netrc::Error:
         Permission bits for '/Users/mhargiss/.netrc' should be 0600, but are 644

I don't want to grant those permissions. :)

[coveralls]

Coverage increased (+0.1%) to 99.21% when pulling a948c5e on mycargus:upgrade-runtime-dependencies into 9175995 on brooklynDev:master.

[mycargus]

Ah, going to have to modify the supported Ruby runtimes too:

There are no versions of rubygems-update (= 3.0.3) compatible with your Ruby & RubyGems
	rubygems-update requires Ruby version >= 2.3.0. The current ruby version is 2.2.0.

New commit incoming...

[sethpollack]

hmm, are we dropping support for those versions of ruby?

[mycargus]

Oh, happy to change it to maintain existing Ruby version support! I was thinking to support the latest of each Ruby minor version, but I'm game for whatever. I think the only exception will have to be 2.2 given rubygems-update requires >= 2.3.0

[sethpollack]

lgtm thanks!