Update requirements.txt

Author: andrew-d

requirements.txt

@@ -1,13 +1,8 @@
-PyYAML==3.10
-cov-core==1.7
-coverage==3.6
-invoke==0.2.0
-mock==1.0.1
-pexpect-u==2.5.1
-py==1.4.13
-pytest==2.3.4
-pytest-capturelog==0.7
-pytest-cov==1.6
-pytest-timeout==0.3
-tox==1.4.3
-virtualenv==1.9.1
+PyYAML==3.12
+coverage==4.4.1
+funcsigs==1.0.2
+mock==2.0.0
+pbr==3.0.1
+py==1.4.33
+pytest-cov==2.5.1
+pytest==3.0.7