Rename gem to "orchestrate"

closes #1
remove date from gemspec, per best practice

It is set automatically when the gem is packaged, and [setting it is
discouraged][gemspec-date].

[gemspec-date]: http://rubygems.rubyforge.org/rubygems-update/Gem/Specification.html#method-i-date-3D
Setup TravisCI integration

Currently just testing against contemporary versions of ruby, but if we want to
setup testing for archaic versions it's trivial.  Rubinius and JVM support
wouldn't be a bad idea.
travis: add 1.9.3
Readme: add travis badge
gemspec: rename to gem name
travis: specify bundler version
travis: postpone 1.9.3 testing for now

There's a problem on 1.9.3 where URI::HTTPS#empty? is being called, and that
isn't actually a method on the URI classes.  Rather than investigate, I'd just
as soon go ahead with the migration to faraday and revisit this later.

For the record, the problem is described in the failing build here:

https://travis-ci.org/orchestrate-io/orchestrate-ruby/jobs/23227310
Merge branches 'mattly/1-rename-gem' and 'mattly/2-travis-integration'