Keybinding improvements

* Bound `nrepl-interrupt` to `C-c C-c` in REPL buffers, to respect Emacs comint tradition.
* Bound `nrepl-load-current-buffer` to `C-c C-c` to respect the common practice to use this keybinding for
a very popular action. Arguably in nrepl nothing is as popular as loading the current buffer.
* `nrepl-switch-to-repl-buffer` now accepts a prefix argument. If one is passed it will take into account the
namespace of the current Clojure source file.
Fixed a typo.
Rebind `C-c C-c` to nrepl-eval-expression-at-point.
Improve compilation error handling

To avoid delays associated with retrieval of the stacktrace, highlighting is
based on the exception message that is reported by the stderr-handler in
nrepl-load-file-handler.  The exception trace is put in the *nrepl-error*
buffer, but not displayed by default.

Adds an nrepl-visit-error-buffer function, to visit *nrepl-error*.

Installs nrepl-jump-to-compilation-error as the next-error-function in
nrepl-interaction-mode buffers, to jump to the compilation error using
next-error.

Adds an optional eval-error-handler to nrepl-make-response-handler.

Adds nrepl-popup-on-error, to control whether stacktraces (globally) are popped
up by default.
Merge pull request #272 from hugoduncan/feature/improve-load-file-on-errors

Improve compilation error handling
Merge pull request #273 from bbatsov/keybindings

Keybinding improvements
Merge #281: Clean up killed connections.
Merge #275 - colorize output sent to nrepl buffer.
Nix interesting "evalulate" typo.

That really should be a word.
Use repl-buffer rather than nrepl-buffer

The use of nrepl-buffer seems ambiguous, so rename to repl-buffer.

Renames to nrepl-repl-buffer, nrepl-create-repl-buffer,
nrepl-check-for-repl-buffer, nrepl-current-repl-buffer.
Allow connections without repl buffers

In order to support tools like lein.el, which use nrepl.el pragmatically, add
the ability to connect without creating a repl buffer.
Merge branch 'master' of https://github.com/kingtim/nrepl.el
Add a hook that runs on load-file completion

The hook allows nrepl.el clients such as ritz and clojure-test-mode to
trigger actions when a file is loaded into the repl session.
Remove only nrepl-note overlays on load-file

When loading a file, only compilation notes are cleared.  This leaves other
overlays intact.
Merge pull request #279 from hugoduncan/feature/allow-no-repl

Allow connections without a repl buffer
Merge pull request #282 from daemianmack/patch-1

Nix interesting "evalulate" typo.
Merge PR #287: nrepl-switch-to-nrepl-buffer no longer working.
Merge branch 'feature/add-file-loaded-hook' of https://github.com/hugoduncan/nrepl.el into hugoduncan-feature/add-file-loaded-hook
Fix checkdoc.
Merge pull request #289 from hugoduncan/feature/clear-only-note-overlays

Remove only nrepl-note overlays on load-file