Ceilometer-api is crashing due to pecan module missing

Moving pecan module listing from test-requires
and test-requires-folsom to pip-requires so that
it can be used by both setup.py and tox.ini

Bug #1102614

Change-Id: I67cd45c068305ec7897d67b425b06173e092b9f8
Merge "Ceilometer-api is crashing due to pecan module missing"