travis for python 3.2, 3.3

 * remove installing debian packages
 * add pytest to requirements
 * change retrieving of python-magic from github in requirements
 * fixes type error for latest python-magic and python 3

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
support python2, python3 of debian package

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>