make tests quieter
toMaple is helpful for debugging
cleanup of update-archive.mpl
clarify a comment (at least for me)
tests using Sample and/or MWC should not be in this file!!
(makes it really hard to debug on some platforms where MWC does not
work in ghci)
minor tweaks to the shape of some of the tests
normal density
Implement:
1. AST simplification
  a. right id rule for >>=
  b. simplification of singleton weight 1 superpose
  c. sorting of superpose (for insuring more deterministic output)
2. recognition of normal density (and normalization factor)
3. simplification of 'useless' last condition on a piecewise
Merge branch 'master' of https://github.com/hakaru-dev/hakaru