Bumps [google-api-client](https://github.com/google/google-api-ruby-client) from 0.11.1 to 0.21....

travis.yml: use Linux and macOS.

And generally cleanup to better match e.g. brew-test-bot.

formulae-analytics: output format tweaks.

- Output 10,000 rather than 1,000 formulae
- Use both batching methods for increased performance...

formula-analytics: handle no formula arguments.

In that case we want to ensure that we still search for something so
provide a single `nil` in t...

formula-analytics: allow specifying multiple formulae.

Allow the specification of multiple formulae on the command-line. This
uses the batched report A...

README: use short docs.brew.sh links.

Allow more categories to be specified

Allow multiple categories to be specified at once and add a new
`--os-version` argument to query...

brew-formula-analytics: handle maximum days ago.

Fixes #9.

brew-formula-analytics: use formulary lookup.

Lookup formulae names from the currently tapped taps to save a little
bit of typing.

Fix RuboCop warnings.

Using the new rules in Homebrew/brew#2679 and check them on new PRs.

Fix Bundler setup

Some more tricks to setup the RubyGems require path properly that will
hopefully survive Ruby ve...

Improve output formatting

- Don't output e.g. `wgetpaste` if you specify `wget` as the formula
- Comma separate counts
- U...

Add JSON output.

Provide a `--json` option to provide JSON output of the data.