Test encoding of pre-compiled non-compressed output

At the time of this commit, the test fails.
When COMPRESS_ENABLE=False and CSS or JS is sent through a precompiler,
the resulting output appears to be encoded using UTF-32.

Signed-off-by: Liam Curry <liam@curry.name>
Encode compiled content when writing it w/o compression

As of #312, the output of compiled content is always unicode.

With ``COMPRESS_ENABLED=True``,
that unicode was piped directly to compression
without writing the intermediate content.
The byte encoding of the compressed content
is handled correctly in this case.

However, with ``COMPRESS_ENABLED=False``,
the unicode content was sent directly to a
``django.core.files.base.ContentFile`` instance,
and somewhere in there
it turned that content into 4-byte-wide characters
resembling UTF-32 encoded content.

This encodes that content using UTF-8
before handing it off to the ``ContentFile``.

This may present an issue in a corner case
where something other than UTF-8 encoding is desired.

Signed-off-by: Liam Curry <liam@curry.name>