Bump the clojure-mode dep to 2.0.0.

clojure-mode 2.0.0 was recently released and it's the first version
that target's nrepl.el exclusively. It makes sense that the
upcoming nrepl.el 0.1.6 should require it, given the fact that many
nrepl improvements were incorporated into it.
added a basic check for an existing REPL buffer in nrepl-jack-in & nrepl
Suppress byte-compilation warning

This takes care of the byte-compilation warning
about a reference to a free variable `paredit-version`.
Fix a couple of docstrings and indentation errors.
Use should instead of assert in tests.
Docstring additions and fixes.
Simplify popup buffer quit/restore using `quit-window'.
Update copyright year and add link to contributors.
Use nrepl-symbol-at-point instead of eldoc-current-symbol for eldoc.
release v0.1.6
bump version
set nrepl-buffer-ns on load so C-c C-n isn't required before evaluation and meta-. work correctly.
Fix ido completion:
1) handle ns-refers in addition to interns
2) don't return a qualified symbol because the other nrepl-read-symbol-name options don't necessarily, and the qualification is wrong for refers
3) eval the callback in the buffer making the request so we can resolve unqualified symbols correctly
Fix #211 - implement jump to error from stacktrace

Now when someone gets a compilation error after `C-c C-k` the top error
of the stacktrace is clickable and it will take the user to the
offending line in the source code. This doesn't work when there is
no source file (say after eval last sexp) for obvious reasons. The functionality
relies on `compilation-minor-mode` being enabled in the error buffer (which is done
automatically after it's created).
Highlight compilation error in the source buffer

The compilation error's line number is extracted from the stacktrace
buffer and highlighted with an overlay in the related source buffer.
The error overlay is cleared upon recompilation. There is some race condition
between the moment in which we start to parse the stacktrace buffer and the moment
the stacktrace has been output to it, therefore the 0.3s sleep to suppress it.
Mention race condition in a comment
Don't underline the blank beginning of the error line
Use font-lock-warning-face as a basis for nrepl-error-highlight-face.
Remove debug message.
Fix function indentation level.