Adding tests for current functionality

- Modified 1 lined of code to allow for better testability
- Added integration tests for app
- Added mock Digital Ocean API
- Added unit tests for Installer (will be changing a lot).

➜  simple-tor-relay git:(rack-tests) ✗ rspec
..........

Finished in 0.07876 seconds (files took 0.46794 seconds to load)
10 examples, 0 failures
Run options:

# Running tests:

Finished tests in 0.020021s, 0.0000 tests/s, 0.0000 assertions/s.
0 tests, 0 assertions, 0 failures, 0 errors, 0 skips
The URL shouldn't be necessary any longer, I've already pulled out the URL from the constructor on master (not sure if you were basing this off your fork or the current master.)