Inline 'in_head.js' and remove from spec helper

We can't reference this file in production. Doing so causes Sprockets to
fail because it tries to interpret the asset but does not have the
a Javascript runtime to do so successfully.

Delete mas_analytics - this is supposed to be a unit test and should
not depend on global objects. We need to start again with this test.
Revert "Remove sprockets dependencies for fonts"

This reverts commit 256a1e7a34da34f569dc631218d7af8e2ef06dd1.