Revert "Merge pull request #762 from zendesk/grosser/content-utf8"

Introduced ad hoc parsing of the Content-Type name attribute, masking a
bug rather than fixing it.

This reverts commit 1aaffe5d6b3e334426bd17107f9296d1173a6d3b, reversing
changes made to 3ce1589a8ca0bc92c7cb076b3e36307a6b9d85df.