Update dependencies from pyup

* Update sphinx from 1.2.3 to 1.4.8
* Update pytest from 2.8.2 to 3.0.3
* Update pytest-timeout from 0.5 to 1.0.0
* Update pytest-cov from 2.2.0 to 2.4.0
* Update pep8 from 1.5.7 to 1.7.0

dev-requirements.txt

@@ -1,8 +1,8 @@
 -rrequirements.txt
 
-sphinx==1.2.3
-pytest==2.8.2
-pep8==1.5.7
+sphinx==1.4.8
+pytest==3.0.3
+pep8==1.7.0
 pytest-capturelog==0.7
-pytest-cov==2.2.0
-pytest-timeout==0.5
+pytest-cov==2.4.0
+pytest-timeout==1.0.0