Merge pull request #163 from StackStorm/upgrade/pip

Upgrade pip from 9.x to currently latest one

Author: armab

Makefile

@@ -41,7 +41,7 @@ venv:
 
 .PHONY: reqs
 reqs: venv
-	$(VENV_DIR)/bin/pip install --upgrade "pip>=9.0,<9.1"
+	$(VENV_DIR)/bin/pip install --upgrade "pip>=19.0,<20.0"
 	$(VENV_DIR)/bin/pip install -r requirements.txt
 	$(VENV_DIR)/bin/pip install -r requirements-test.txt
 	$(VENV_DIR)/bin/pip install -r requirements-docs.txt