Minor changes in virtualenv setup file names

Moved the requirements.txt setup files into a namespace
called .virtualenv in order to stay compatible with the
.travis requirement files

.virtualenv.dev-requirements.txt

@@ -8,7 +8,7 @@
 # After activation of the env, install it with:
 # $ pip install -r dev-requirements.txt
 
--r requirements.txt
+-r .virtualenv.requirements.txt
 
 # virtualenv-based automation of test activities
 tox

MANIFEST.in

@@ -1,6 +1,4 @@
-#
-#
-#
+# Manifest describing source package contents
 
 graft boot
 graft config
@@ -19,6 +17,7 @@ include .landscape.yml
 include .travis*
 include .releasetags
 
-include *requirements.txt
+include .virtualenv.requirements.txt
+include .virtualenv.dev-requirements.txt
 
 global-exclude *.py[cod] __pycache__ *.so *.dylib