Support per-project overrides.
Use shell=True on Windows. Required to find cpplint within PATH.
Feed file path to the cpplint, not just a string.

CppLint relies on finding the corresponding header file in the same
directory for some checks. Feeding the string breaks the feature and
is most likely less efficient.
Fix responsiveness problems caused by linting all files on start.

Do not lint inactive buffers when they load and add an on_activate listener
to trigger linting when buffer is activated to account for the former.
Might want to drop it
Revert pyflake updates