chore(wallaby): remove wallaby.js configuration
chore(wallaby): remove wallaby.js configuration

Removes wallaby.js configuration file as it is user-specific and does not
belong inside the main repo. I have externalized the config into a gist
available at https://gist.github.com/TylorS/d919bccf408f71f94953.

Closes #12

motorcyclejs/core