Fix for issue #1 and issue #2

A new module mime-headers was extracted in order to deal with non-ASCII
text in headers. This extracted module also simplified the process of
adding support for the Content-Disposition header (which benefits from
non-ASCII support in the case of filenames)
Merge branch 'issue-1' into 0.1.1
Update package.json for 0.1.1 release
Release 0.1.1