Fix omnisharp-rename-interactively crashing

It would complain "all-solution-files is not a symbol".
Presumably the variable is not accessible to tags-query-replace when
tags-query-replace is evaluated. So I made the variable a global
variable instead. I don't like globals at all, but at least now it
works.
Improve function argument naming
Add Cask file
Setup tests for Cask
Merge remote-tracking branch 'remotes/github/master' into develop
Bump version 2.9 -> 3.0
Add a bash script for running all tests with ert-runner
Fix failing "get server executable command" test (win version)

Apparently some stuff is required to properly quote the paths needed for
the command - that are only available on the windows version of emacs.
I mocked them out :)
Rename unit test file
Whitespace fixes
Add basis for integration tests
Remove explicit (require)s from unit-test file
Add basis for running integration tests
Add integration test for omnisharp-fix-usings

It currently requires the omnisharp server to be running, but it works!
Allow evaluating anything in tests

Yeah I guess this is pretty cheap! Let's not overdo it. It works
beautifully for running M-x functions even though it could do anything.
Remove superfluous keybinding from fix usings test
Test that ambiguous /fixusings are shown to the user
Give fix-usings integration tests a better file name
Add integration tests for auto-complete features using popup.el
Add helper script for starting emacs in the project environment