install dev and main dependencies together (#138)

this is to avoid hiding version conflicts

Author: de-code

Makefile

@@ -47,8 +47,9 @@ venv-create:
 
 dev-install:
 	$(PIP) install -r requirements.build.txt
-	$(PIP) install -r requirements.dev.txt
-	$(PIP) install -r requirements.txt
+	$(PIP) install \
+		-r requirements.dev.txt \
+		-r requirements.txt
 
 
 dev-venv: venv-create dev-install