Travis, badges, licenses and more

[baszalmstra]

This PR adds:

• A usable .travis.yml, although the build fails because tests cant run on Linux yet.
• A copying file that contains info on licenses
• A travis build badge
• A docs website link
• A license badge
• A discord badge
• A lines of code badge
• Also contains a build fix for macOS regarding slashes in cargo.toml
• A fix for submodules and forks, it now also references the mun-lang org in the url.

[baszalmstra]

Set up travis CI builds