Remove the Pygments dependency

[vmg]

This PR removes the Pygments dependency on Linguist.

cc @aroben @bkeepers

[aroben]

This probably needs to be v4.0 since it breaks compatibility right?

[vmg]

Meh, semver is a dumb concept overall. I'm not opposed to bumping the major version anyway. @bkeepers are you OK with it?

[aroben]

I think we can remove all the lexer attributes in the YAML file too.

Meh, semver is a dumb concept overall. I'm not opposed to bumping the major version anyway. @bkeepers are you OK with it?

I think we need to bump it so people specifying gem "linguist", "~>3.5" don't end up with an incompatible version.

[vmg]

Word. Gonna clean the yaml.

[pchaigno]

There should maybe be some documentation on the new syntax highlighting(?). Many people come here with questions and issues about this.

[qerub]

Any chance GitHub could use a version without this change until #1721, #1717, #1670 and perhaps more are resolved?

[vmg]

I'm afraid that's not an option. :)

[aroben]

@qerub The main problem with rolling back to Pygments is that we wouldn't discover any more of these issues, and thus wouldn't be able to fix them. We're working to fix these problems as quickly as they're discovered, but it just isn't possible to find all the bugs with these grammars without using them live on github.com. Sorry for the inconvenience in the meantime.