adds a requiremnts.txt file for the project

With the addition of the validate module we need to ensure
that notario is installed. This will be done with the use
of this requirments.txt file and pip.

Signed-off-by: Andrew Schoen <aschoen@redhat.com>

requirements.txt

@@ -0,0 +1,2 @@
+ansible>=2.4.2
+notario>=0.0.13