Update pip before running through requirements

pip uses python-requests. In jessie the system version is 2.4.3 but
requirements.txt wants 2.7.0. the system version of pip (1.5.6) can not use
the 2.7.0 version of requests so pip must be updated before we start pulling
down other requirements that may end up with a newer version of requests.

main.yml

@@ -13,6 +13,7 @@
     - apt: name=python-pudb state=present
     - apt: name=python-pip state=present
     - apt: name=python-mysqldb state=present
+    - shell: pip install -U pip
     - shell: pip install docker-py==1.1.0
 
     # requirements