Sort requirement files in alphabetical order

This makes code more readable, and can check whether specific library
in the requirement files easily. We also enforce the check in pep8.

Change-Id: I032c3c3d29522ce85f64b21d6428d975e46cc701
Closes-Bug: #1285478

requirements.txt

@@ -1,30 +1,30 @@
-pbr>=0.6,!=0.7,<1.0
-pycrypto>=2.6
+argparse
+Babel>=1.3
 eventlet>=0.13.0
 greenlet>=0.3.2
 httplib2>=0.7.5
 iso8601>=0.1.9
 kombu>=2.4.8
-argparse
 lxml>=2.3
 netaddr>=0.7.6
-six>=1.5.2
-sqlalchemy-migrate>=0.8.2,!=0.8.4
-python-novaclient>=2.17.0
+oslo.config>=1.2.0
+paramiko>=1.9.0
 PasteDeploy>=1.5.0
-requests>=1.1
-Routes>=1.12.3
-SQLAlchemy>=0.7.8,<=0.9.99
-WebOb>=1.2.3
-python-heatclient>=0.2.3
-python-keystoneclient>=0.7.0
-python-swiftclient>=1.6
-python-neutronclient>=2.3.4,<3
+pbr>=0.6,!=0.7,<1.0
+pycrypto>=2.6
 python-ceilometerclient>=1.0.6
 python-cinderclient>=1.0.6
+python-heatclient>=0.2.3
+python-keystoneclient>=0.7.0
+python-neutronclient>=2.3.4,<3
+python-novaclient>=2.17.0
+python-swiftclient>=1.6
 python-troveclient>=1.0.3
 PyYAML>=3.1.0
-paramiko>=1.9.0
-Babel>=1.3
-oslo.config>=1.2.0
 qpid-python
+requests>=1.1
+Routes>=1.12.3
+six>=1.5.2
+SQLAlchemy>=0.7.8,<=0.9.99
+sqlalchemy-migrate>=0.8.2,!=0.8.4
+WebOb>=1.2.3