Add listener and event handler registration (close #130)

This introduces registerListener and registerEventHandler to the support
code helper. Those two methods let clients register custom listeners for
AST events.

Relates to #91.
Typo
Release 0.3.2
Bump CoffeeScript
Bump connect
Bump cucumber-html
Bump gherkin
Bump jasmine-node
Bump mkdirp
Bump nopt
Bump pogo
Bump rimraf
Bump underscore
Bump walkdir
Add durations to JsonFormatter (close #125 #139)
DRY
Add contributor
Output step definition snippets in CoffeeScript
Refactor
Add contributor