print out full usage info in case of invalid option
print out full usage info in case of invalid option

fixes #350

spinda/liquidhaskell,Kyly/liquidhaskell,Kyly/liquidhaskell,Kyly/liquidhaskell,rolph-recto/liquidhaskell,abakst/liquidhaskell,rolph-recto/liquidhaskell,spinda/liquidhaskell,abakst/liquidhaskell,rolph-recto/liquidhaskell,rolph-recto/liquidhaskell,spinda/liquidhaskell,abakst/liquidhaskell,abakst/liquidhaskell,abakst/liquidhaskell,rolph-recto/liquidhaskell,spinda/liquidhaskell,Kyly/liquidhaskell,mightymoose/liquidhaskell,mightymoose/liquidhaskell,Kyly/liquidhaskell,rolph-recto/liquidhaskell,mightymoose/liquidhaskell,spinda/liquidhaskell,mightymoose/liquidhaskell,Kyly/liquidhaskell,abakst/liquidhaskell,mightymoose/liquidhaskell,mightymoose/liquidhaskell,spinda/liquidhaskell