Add tests and get ssz impl comply with the current spec (#102)

* Add new uint tests

* Check deserialization for uint

* Align ssz to the newest dev spec

* Fix derive for new spec

* Check in prefixable

* Chunkify

* Add test for chunkify

* Add merkleize and tests

* Add bytes impl for hash

* Add tuple tests

* Fix derive hashing

* Add description for ssz and ssz-derive

* Remove debug println

* Fix build

* Add version for ssz

* Fix whitespace typo

* Fix breakage due to nightly 2019-03-18

* Remove rust toolchain file