clojure-mode-version was not updated for release of 5.6.0

[rwhogg]

Expected behavior

The variable clojure-mode-version should match the release number.

Actual behavior

The variable clojure-mode-version remains at 5.5.2 instead of 5.6.0.

Steps to reproduce the problem

This can be observed by inspection. See https://github.com/clojure-emacs/clojure-mode/blob/master/clojure-mode.el#L82

Environment & Version information

clojure-mode version information

clojure-mode (version 5.5.2)

Note that this is using the latest code from master.

Emacs version

Aquamacs 3.3 (based on GNU Emacs 25.1.1)

Operating system

macOS El Capitan

[dunn]

#417