Remove unittest2py3k dependency from setup.py

unittest2py3k is not required for twilio to function correctly and it
can intefere with standard unittest functionality like expectedFailure
and skip

Author: Ian Foote

setup.py

@@ -18,7 +18,6 @@
 if sys.version_info < (2, 6):
     REQUIRES.append('simplejson')
 if sys.version_info >= (3,0):
-    REQUIRES.append('unittest2py3k')
     REQUIRES.append('socksipy-branch')
 
 setup(