chore(dependancies): add `copy-paste` package as dependancies

https://github.com/xavi-/node-copy-paste
feat(copy.message): copy error message on click #78

https://github.com/AtomLinter/Linter/issues/78
style(status.bar): change cursor to pointer on `.error-message`
refactor(status.bar): refactor `statusbar-view` to make it testable
test(status.bar): add tests for statusbar-view
refactor(status.bar): refactor spec
Merge pull request #80 from AtomLinter/copy-statusbar-message

Copy statusbar message