add the ListT constructor to the valid STypes since TH also has this special type
complete the definition of thTypeToSType
cleanup
Rewrite getClassEnv using Data.Set to make it slightly faster. And ...

... add comment about slow compilation if all instances and classes
are considered when finding the relevant classes.
remove TemplateHaskell language pragma
move testing code to Test.hs
Add profiling flag and temporarily make all modules visible for easy debugging