Add explicit setup of expected namespaces

When connecting to an nrepl server, explicitly require clojure.pprint, and
use clojure.repl/doc.  When used with an nREPL server that didn't match
these assumptions, nrepl.el commands otherwise fail.
Add convenience bindings to clojure-mode-map for starting nrepl

Since people are generally in some Clojure buffer when starting
nrepl.el it's useful to have convenient keybindings for that in
`clojure-mode-map`. The mnemonic for the keybindings are `j` for jack-in
and `c` for connect. The keybindings are autoloaded and added to
`clojure-mode-map` after `clojure-mode` has been loaded.
New customization variable: nrepl-popup-stacktraces-in-repl

We use nrepl-popup-stacktraces only non-REPL buffers, and introduce a
specific flag for the latter.
Add travis checkdoc configuration

Note, the build currently fails.
Fix all checkdoc issues.
Merge pull request #262 from hugoduncan/feature/add-travis-checkdoc

Add travis checkdoc configuration
CHANGELOG and README entries for nrepl-popup-stacktraces-in-repl
Merge pull request #232 from bbatsov/clojure-mode-map

Add convenience bindings to clojure-mode-map for starting nrepl
Merge branch 'feature/add-aux-requires' of https://github.com/hugoduncan/nrepl.el into hugoduncan-feature/add-aux-requires
Checkdoc fixes.
Merge branch 'hugoduncan-feature/add-aux-requires'
Merge pull request #259 from jaor/local-popup

Allow local values for nrepl-popup-stacktraces