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
Nit: Can just do File.read instead