1. Remove ember-cli-clipboard dependency
2. Provide a new copy-button component implementing the same
interface as ^ but make the clipboard functionality injectable
3. Provide 2 implementations of a Clipboard. One using clipboard.js (as
previously) and an additional local storage 'clipboard'.
4. add a BDD step to assert whats in the clipboard (the fake one)
Main reason here is that `document.exec` must be called by a user
interaction
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