Add `config.cacheDirectory` for customizing where the node-haste cache files go

Currently the node-haste cache files always go into the
jest/src/.haste_cache_dir directory. This is awkward and sometimes
doesn't work for certain people (like if you install jest globally into
a read-only dir, for ex).

This adds a new `config.cacheDirectory` option that allows for
customizeability here.