v0.5.0

• Add method to serialize metrics to ostream (thanks Patrick Gansterer [email protected])
• Fix summary text format (thanks Brian Hong [email protected])
• Add gzip compression support (thanks Gregor Jasny [email protected])
• Fix Readme typos (thanks Mateusz Piotrowski [email protected])
• lots of CMake and Bazel fixes (thanks again, Gregor Jasny [email protected])