Fix nrepl-connections-buffer-mode-map

Define the mode-map before defining the mode, so the defvar actually
gets initialised rather than having the mode define it as empty.
Fix usage of nrepl-nrepl-buffer
Remove obsolete function nrepl-stacktrace

The function is no longer used after the changes
@hugoduncan made recently.
Fix broken test.
Merge pull request #306 from bbatsov/remove-obsolete

Remove obsolete function nrepl-stacktrace
Default to event logging disabled.
Merge branch 'master' of github.com:kingtim/nrepl.el
Merge remote-tracking branch 'kingtim/master' into ns-fix6