Chomp the .deb control file before writing out Packages.gz.

Some debs (RStudio *cough*) have an extra newline at the end of their
control file.  This makes for a Packages.gz file with syntax errors,
which in turn breaks apt-get update.  Not sure if it's a bug on the
packager's part, but this patch does get around that problem.
Merge pull request #31 from saintaardvark/fix_extra_newline_in_deb_description_field

Chomp the .deb control file before writing out Packages.gz.