kill Strings
make more things Symbols to hide internals
symbolize all the things
blah
ugh
blah
better hashing?
hide repr of Symbol
Merge branch 'master' of github.com:ucsd-progsys/liquid-fixpoint into text-symbol

Conflicts:
	src/Language/Fixpoint/Types.hs
Merge pull request #39 from ucsd-progsys/text-symbol

Use Text instead of String. fixes #37