refactor: Move context setup into testactular.js

Context doesn't need a separate js, it just needs a method in testacular.js to call.
Merge pull request #310 from bitwiseman/fix-setup-context

refactor: Move context setup into testactular.js
chore: fix git commit-msg hook to work with git gui

Because git gui uses `GITGUI_EDITMSG` instead of `COMMIT_EDITMSG`.