feat(compliance): Add JSON output option

This adds a new --json flag to the compliance subcommand, which
will output the compliance test results as minified JSON to stdout.

Also a few other small additions:
- Exit 1 if compliance tests fail
- Use random port for test server using freeport library (added)

Signed-off-by: Josh Dolitsky <393494+jdolitsky@users.noreply.github.com>

WORKSPACE

@@ -1072,6 +1072,13 @@ go_repository(
     version = "v0.0.0-20160315200505-970db520ece7",
 )
 
+go_repository(
+    name = "com_github_phayes_freeport",
+    importpath = "github.com/phayes/freeport",
+    sum = "h1:JhzVVoYvbOACxoUmOs6V/G4D5nPVUW73rKvXxP4XUJc=",
+    version = "v0.0.0-20180830031419-95f893ade6f2",
+)
+
 go_repository(
     name = "com_github_pquerna_otp",
     importpath = "github.com/pquerna/otp",