Small doc, CI and modules updates

[bzz]

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A small drive-by improvements:

• doc: link for CI badge change to .com to fix image rendering in README

  Before After

• CI updated to include 2 latest profiles, following src-d Go conventions for libraries

• go module definition for gopkg.in/src-d/go-errors.v1 added This way, downstream Go 1.11+ clients can benefit from a module-awareness. It's not mandatory and CI now includes several profiles, to make sure it works with and without modules. Comes with affordable CI build time increase: before: 1 min 7 sec, after 1 min 52 sec