Provide wildcard matching for syntax groups

[meatbody]

Currently linters are defined to match a specific syntax or list of syntaxes. If a file is considered to be a subtype of a given syntax, this causes the linters to no longer match the file. A concrete example: linter-pylint has its syntax set to 'source.python'. The package atom-django offers some useful snippets for Django-specific files, defining the syntax 'source.python.django'. However, setting a file to this syntax causes linter-pylint to no longer recognize the file.

From a quick inspection, it looks like this is controlled by initLinters in lib/linter-view.coffee, which looks to be doing exact matching on the syntaxes (as expected). It would be nice to provide a wildcard option (e.g. 'source.python.*') so linters don't have to anticipate every sub-syntax.

[davidtheclark]

Another nice possibility would be to be able to expose a setting so that the user can add syntaxes. (Is this already possible? I was trying to do it and couldn't figure out to make it work ...)