Don't include 'test' in bower install

[pimterry]

Currently when installing the package with bower it complains that you don't have an 'ignore' property:

bower heap#~0.2.6         invalid-meta heap is missing "ignore" entry in bower.json

Now added this, both to stop the warning, and to actually ignore the tests directory (which currently gets downloaded and included locally whenever you depend on heap.js)

[pimterry]

Nudge. Would be nice to merge this.