Bitfield/ rle+ impl

[austinabell]

Summary of changes
Changes introduced in this pull request:

• Adds bitfield with RLE+ encoding through serde cbor serialize and deserialize implementations
  • Implementation was done by @dignifiedquire for the RLE+ encoding and decoding, I just updated to follow new protocol (encoding version), bumped versions, and implemented serde traits

The BitVec API is good but follows the Vec interface very closely where setting bits it will panic when out of range so when using you have to resize manually when necessary

Reference issue to close (if applicable)

Closes #276

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