Unused import
Apparently there is no need for separate linter_can_lint method now
clear() can be an instance method.
Remove trailing space and period from error messages
Oops, missed an argument
Need to add '.exe' on Windows
Added ability to specify in SublimeLinter settings extra platform-specific paths to be added to $PATH when searching for an executable

Also tuned the lru_cache sizes a bit in lint.util.
Make keys more specific to SublimeLinter
Automatically amend the current color scheme with SublimeLinter colors if necessary.

Whenever the Sublime Text user preferences change, the current color scheme is checked to see if it has the SublimeLinter color entries. If not, they are added to a copy of the color scheme in Packages/User, and the copy is set as the current scheme.
Use sublime.platform() since it's specific to the platforms ST supports