update requirements workflow

requirements-to-freeze.txt

@@ -0,0 +1,3 @@
+pytest
+pytest-cov
+pytest-httpbin

requirements.txt

@@ -1,6 +1,14 @@
-py==1.4.30
-pytest==2.8.1
-pytest-cov==2.1.0
-pytest-httpbin==0.0.7
-httpbin==0.4.0
-wheel
+coverage==4.0.3
+decorator==4.0.9
+Flask==0.10.1
+httpbin==0.4.1
+itsdangerous==0.24
+Jinja2==2.8
+MarkupSafe==0.23
+py==1.4.31
+pytest==2.8.7
+pytest-cov==2.2.1
+pytest-httpbin==0.2.0
+six==1.10.0
+Werkzeug==0.11.4
+wheel==0.29.0