chore(deps): Link requirements.txt within requirements_dev.txt

This way I only have to run pip once to get ALL the deps
installed. I'm lazy I know.

Author: clarete

Makefile

@@ -2,7 +2,7 @@ run:
 	@python server.py
 
 setup:
-	@pip install -r requirements.txt -r requirements_dev.txt -U
+	@pip install -r requirements_dev.txt -U
 
 setup-prod:
 	@pip install -r requirements.txt

requirements_dev.txt

@@ -1,3 +1,4 @@
+-r requirements.txt
 coverage>=4.5.1,<4.6.0
 flake8>=3.6.0,<3.7.0
 nose>=1.3.7,<1.4.0