Release version 1.3

This version bump enables the use of OpenAPIv2 annotations along with various
bugfixes. It also fixes grpc-gateway to work with recent versions of gRPC.

Add changelog for 1.2.2

generated with github_changelog_generator

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compare-link=false
issues=false
future-release=v1.2.2

Add changelog for 1.2.1

generated with github_changelog_generator

author=false
compare-link=false
issues=false
future-release=v1.2.1

Add changelog for 1.2.0

generated with github_changelog_generator

author=false
compare-link=false
issues=false
exclude-tags=v1.2.0.rc1
future-release=v1.2.0

Various updates, corrected include path to README.md

Merge pull request grpc-ecosystem#191 from tmc/tmc.better_eof_handling

return err early if EOF to prevent logging in normal conditions

Merge pull request grpc-ecosystem#184 from gengo/feature/browser-example

Add browser examples