WIP: Start preparing release v3.0.7 (#147)

* Use ooni/probe-engine 0.16.0
* Update all the other dependencies
* Use GitHub Actions rather than Travis CI
* Automatically build and test binaries on the target OS (for Windows, macOS, Linux on amd64)
* Make sure we correctly measure coverage
* Make sure we use `-race` when running tests
* Remove unnecessary scripts
* Make sure the README is up-to-date
* Write small script to update binary data and add GitHub Actions checks for it
* Notice that we needed to run ./updatebindata.sh and run it
* Self documenting instructions regarding cross compiling
* Set version number to v3.0.7-beta

Part of https://github.com/ooni/probe-engine/issues/748

updatebindata.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -ex
+go get -u github.com/shuLhan/go-bindata/...
+gobindata=`go env GOPATH`/bin/go-bindata
+version=`$gobindata -version | grep go-bin | cut -d ' ' -f2`
+if [ "$version" != "3.3.0" ]; then
+  echo "FATAL: unexpected go-bindata version" 1>&2
+  exit 1
+fi
+$gobindata -nometadata -o internal/bindata/bindata.go -pkg bindata data/...