Sync test-requirements with global requirements

requirements.txt in hacking coordinates the installation order
of pep8, flake8 and pyflakes as other projects do.

Change-Id: I3b4e8ee88ba01d0ba917b8e968ebabec74a554ab

test-requirements.txt

@@ -1,13 +1,9 @@
-# Install bounded pep8/pyflakes first, then let flake8 install
-pep8==1.4.5
-pyflakes==0.7.2
-flake8==2.0
-hacking>=0.5.6,<0.7
+hacking>=0.5.6,<0.8
 
 cliff-tablib>=1.0
 coverage>=3.6
 discover
-fixtures>=0.3.12
+fixtures>=0.3.14
 mox>=0.5.3
 python-subunit
 sphinx>=1.1.2