Made compiler functions instance methods.
Added more standard functions.
Added initial set of expression functions.
Added Status object for state persistence
Added previous exit code to required args
Merge branch 'master' of github.com:ltn100/prompty
ommit's message is:

Made compiler functions instance methods.
Added more standard functions.
Added initial set of expression functions.
Added Status object for state persistence
Added previous exit code to required args

Made compiler functions instance methods.
Added more standard functions.
Added initial set of expression functions.
Added Status object for state persistence
Added previous exit code to required args

Conflicts:
	prompty.py