Start testing the flapping plugin
Allow flapping plugin to retry indefinitely

Change the behavior of the flapping plugin's max_retry option to follow
the same convention as the global max_retry option. If the option is set
to -1, we keep retrying forever. Issue #519
Add assertion to window test
Add myself to NOTICE
Ignore Vim backup files
Merge pull request #535 from amarandon/flapping

Allow flapping plugin to retry indefinitely