Pin test-requirements

to avoid problems from new versions and to support old versions of
Python

- waitress==1.0.0 stopped supporting Python 2.6
- pytest-pep8==1.0.3 seems to have broken Python 3.4?

test-requirements.txt

@@ -1,4 +1,16 @@
-pytest
-pytest-capturelog
-pytest-pep8
-waitress
+apipkg==1.4
+appdirs==1.4.0
+execnet==1.4.1
+packaging==16.8
+pep8==1.7.0
+py==1.4.32
+pyparsing==2.1.10
+pytest==2.9.2
+pytest-cache==1.0
+pytest-capturelog==0.7
+pytest-pep8==1.0.2
+requests==2.13.0
+requests-unixsocket==0.1.6.dev7
+six==1.10.0
+urllib3==1.20
+waitress==0.9.0