Add 'dev' extras

Signed-off-by: Vasilis Tsiligiannis <acinonyx@openwrt.gr>

setup.cfg

@@ -63,6 +63,18 @@ install_requires =
     satnogsdecoders~=0.0
     simplejson~=3.16.0
 
+[options.extras_require]
+dev =
+    pytest-cov~=2.5.0
+    pytest-django~=3.1.0
+    pytest-forked~=0.2.0
+    pytest-xdist~=1.22.0
+    mock~=2.0.0
+    Faker~=0.8.0
+    factory-boy~=2.10.0
+    pur~=4.0.0
+    docopts~=0.6.0
+
 [flake8]
 max-complexity = 23
 max-line-length = 99