A bunch of stuff 🐸

Here's some stuff I accumulated over time, let me know if you want to
cherry-pick just some stuff.

### PR #85 
- [x] Using System Ruby 1.8

### PR #88 
- [x] Switch command now tries to infer the subject from the filename when creating a new spec file

### PR #83 
- [x] Use <kbd>⌃⌥⇧↓</kbd> for alternate file (fixes #57)

### PR #82 
- [x] Describe and Describe Type snippets now try to infer the subject from the filename
- [x] Add `.sh⇥` that expands to a full `should` syntax with tab stops (with drop down to choose between "should" and "should_not")
- [x] Add `.ex⇥` that expands to a full `expect` syntax with tab stops (with drop down to choose between "to", "not_to" and "to_not")
- [x] Alias `.ex⇥` as <kbd>⇧⌃W</kbd> wrapping current word within a full `expect` with tab stops
- [x] Add `dc⇥` to `described_class`
- [x] Add `sp⇥` to `save_and_open_page` (Capybara)
- [x] Add more tab stops to `before` and `after`
- [x] Other minor fixes
- [x] Fix alternate file for TM2 (#38)