Make Bool_ Typeable
Updated tests to pass
Cleanup exports
First pass at priors and gibbs proposal generation
remove some warnings
comment out tests that ought to be moved elsewhere
hand merge
Removing Typeable constraints in interpretations

- Removing the constraint wherever it is used
  only for casting Either a b to Either () ()
Merge remote-tracking branch 'origin/master'
Adding condition as helper
add erf to the language.  Implement disintegrate of if_ too.
hand merge, and add erf to language, and implement disintegrate of if_.
comment out unecessary import
both repr Real and repr Prob are Fractional
only a single test now properly fails, with 4 ignores to get back to.
implement a couple of missing instances