Merge branch 'refactor/environmental-generic-traits' into refactor/substrate-state-machine-generic

* refactor/environmental-generic-traits:
  whitespace
  Teach environmental! about generics
  Validator side of the collation protocol. (#295)
  Improve Wasm extern errors and increase heap (#299)
  Issue 212 - refactor Checkable trait to be more generic (#287)
  Fix for nightly 2018-07-10 (#296)
  PoC-2 tweaks (#293)