Simplify popup buffer quit/restore using `quit-window'.
Update copyright year and add link to contributors.
Merge branch 'popup-refactor'
Fix #199 - make *nrepl-src* closable with 'q'

`nrepl-popup-buffer-mode` was misbehaving originally, but the recent
refactoring of the popup window quit/restore logic fixed the problem
and now it's ok to use `nrepl-popup-buffer-mode` together with
`*nrepl-src*`.
Merge pull request #230 from bbatsov/fix-199

Fix #199 - make *nrepl-src* closable with 'q'
Use nrepl-symbol-at-point instead of eldoc-current-symbol for eldoc.
release v0.1.6
bump version