Remove vary-meta test from persistent-map-test

  Vary-meta is composed of functions from the meta interface. This
  composition is already tested by meta-test.
Merge pull request #66 from patrickgombert/remove-old-test

Remove vary-meta test from persistent-map-test
Merge pull request #67 from patrickgombert/bit-ops

Bit ops
Add bit-ops

  Added bit-shift-right, bit-clear, bit-set, bit-flip & bit-test