v1.1.0

Notable changes:

• The serialization logic (for both Marshal and Unmarshal) has been optimized. Testing inside Google demonstrate that the new implementation is about 1.3x to 2.1x faster.
• protocolbuffers/protobuf#272 Unknown fields in proto3 are now preserved.
• #472 JSON marshal and unmarshal now check for proto2 required field.
• #483 GetExtension returns the raw bytes if the ExtensionDesc does not have type information.
• #499 Invalid UTF-8 in string types are rejected during marshal and unmarshal.
• #511 Fields of bad wire types are treated as unknown fields instead of an error.
• #544 The protoc-gen-go generator supports the paths=source_relative option.
• #561 Unknown fields in map entries are now ignored instead of causing an unmarshal error.
• #583 The "import public" feature is now implemented using Go type aliases.

v1.0.0

proto: add DiscardUnknown function (#498)

This copies the discardLegacy logic from the dev branch.
The unit tests are located on the dev branch and will be merged
into the master branch in the near future.

This function is cherrypicked into master in order to support the
master to dev transition.