Store cache in node_modules folder

[tschaub]

Store the cache in a .cache folder in node_modules/grunt-newer/

That way it's already ignored by most projects and it's removed on upgrade, which is a good thing in case you change the format or something.

[tschaub]

I like the suggestion. I was following the discussion on https://github.com/gruntjs/grunt-contrib/issues/132 and the documented suggestion to use .grunt/[npm-module-name] directory. But I'll admit I haven't seen anybody else doing the same.

There is currently an undocumented timestamps option that makes this location configurable. But I like the default of using a path relative to the install itself.

Somewhat unrelated, but for configurations with dest files, the timestamp files can be avoided in favor of checking the mtime of the dest file. Need to try this out at some point.