Change "after" methods in tests to "teardown"

Simplecov was showing these two lines weren't running in the test suite.
Minitest expects "setup"/"teardown", not "setup"/"after".
Add test cleanup code to edit_test

ENV['EDITOR'] previously wasn't backed up by test setup.
Ignore .ruby-version
test RemoteInterface

- add tests for RemoteInterface#read_command
  - indirectly tests RemoteInterface#readline
- add tests for RemoteInterface#close
  - indirectly tests Interface#errmsg
- add tests for RemoteInterface#confirm
  - indirectly tests Interface#confirm
Change RemoteInterface tests to be more granular

- Organize method tests into their own test classes
- use Minitest::Mock#stub instead of Minitest::Mock#expect when an
expectation isn't needed
Update RemoteInterfaceTest to satisfy rubocop style guidelines
Change mocking style from Minitest to Mocha
Merge pull request #88 from eric-hu/remote_testing

Remote testing