Put .sagui cache in node_modules/.cache

[xaviervia]

This makes the cache folder automatically ignored by git and it is the common practice for cache folders.

[deepsweet]

Also it will be cached by Travis across builds with the default configuration for caching with Node, so no additional config lines are needed.

[pirelenito]

oh! that is quite neat idea.

[deepsweet]

might be interesting https://github.com/avajs/find-cache-dir