Add modules support and bump version up to 3.0.0. (google#292)

* Add modules support and bump version up to 3.0.0.

deflaking (google#265)

* remove logspam

* more logspam

* more logspam

Merge pull request google#25 from google/proxy-binary

examples/main: move to cmd/proxy and support as de facto proxy binary.

Merge pull request google#19 from google/readme-updates

Readme updates

Merge pull request google#11 from google/consistency

Consistency