add --test flag to Meteor CLI for velociy CI support

- establish a DDP connection to Meteor
- subscribe to test results
- hit running web server
- exit with appropriate status code after tests have completed
clean up velocity --test pull request

- remove hardcoded localhost:3000
- add documentation to command
- remove emoji
Move velocity code to a separate file for easier maintenance.
Mark run --test as experimental.
comments
code style cleanups to match style guide.
help text nitpicking.
Merge branch 'pr-2680' into devel