Added changelog for about to be published version with migration guides
for changes that might be considered unexpected.

I made most of the `CHANGELOG.md` changes 2 August, but did not push the
version to npm until 7 August. Updating the changelog just in case anyone
updates and looks back on the changelog for clues of when things happen.

I'm sorry. :see_no_evil:

This reverts commit 2f51083565. Util is
not yet configurable, so issue links point to `mocha`.

The goal is to reduce the number of files downloaded by ignoring the test directory

Removed cache* functions altogether. mustache.parse is all that's
really needed.

This commit allows pre-compiled templates to be executed without
keeping the original template around. It is still required when using
higher-order functions.

Fixes #262

Fixes #247

Text tokens now accurately reflect their content's exact position
in the original template.

Fixes #207 #210

Also, allow partials to be passed to the function that is returned
for pre-compiled templates. This makes the API more consistent all
around, but comes with the caveat that renderers are much more
aggressive at caching. Now, any time a template or partial is
compiled with the same name as a previously compiled template the
cached version is used.

Fixes #240