Add a command to cycle parentheses () -> [] -> {}

[nbfalcon]

lispy-cycle-parens will cycle parentheses () -> [] -> {} for the list at
point. {} only works in clojure-mode.

Currently, there is no keybinding.

[coveralls]

Coverage decreased (-62.8%) to 0.0% when pulling ee7cf40 on nbfalcon:feature/lispy-cycle-parens into 38a7df4 on abo-abo:master.