Split dependencies into test and dev.

Not all dependencies are required for running tests so we shouldn't
be requiring our CI environment to install them right?

Author: dave-shawley

dev-requirements.txt

@@ -1,6 +1,5 @@
+-r test-requirements.txt
 flake8>=2.2,<3
-coverage>=3.7,<4
-nose>1.3,<2
 pyflakes>=0.8,<1
 sphinx>=1.2,<2
 sphinx-rtd-theme>=0.1,<1

test-requirements.txt

@@ -0,0 +1,2 @@
+coverage>=3.7,<4
+nose>1.3,<2