Tag a release + update docs

[Code0x58]

I had to use commit = "7e6890ff5f806dcc3790b86e4acfed9ad3a82ee7" instead of tag = "0.3.0" in the load(…) as the tag is out of date (from 2016, 28 commits ago) and misses changes for bazel 0.6.0 compatibility.

The docs say to use the tag 0.3.0, so it would be good to update the docs at the same time.