Rather than using .lint.py files that contain a LINTER object, linter definitions are now in
standalone .yml files. In the case of external linters that need to run python code, the payload
is now of the form:
<module path>:<object path>
The <module path> is the import path to the module, and <object path> is the callable object to
use within that module. It is up to the consumer of mozlint to ensure the <module path> lives on
sys.path. For example, if an external lint's function lives in package 'foo', file 'bar.py' and
function 'lint', the payload would read:
foo.bar:lint
This mechanism was borrowed from taskcluster.
MozReview-Commit-ID: AIsfbVmozy4
