Update requirements-dev to latest versions used on travis runs

Author: dpkp

requirements-dev.txt

@@ -1,15 +1,15 @@
 flake8==3.4.1
-pytest==3.4.0
-pytest-cov==2.5.1
+pytest==3.10.0
+pytest-cov==2.6.0
 docker-py==1.10.6
-coveralls==1.2.0
+coveralls==1.5.1
 Sphinx==1.6.4
-lz4==0.19.1
-xxhash==1.0.1
-python-snappy==0.5.1
-tox==2.9.1
-pylint==1.8.2
-pytest-pylint==0.7.1
-pytest-mock==1.6.3
+lz4==2.1.2
+xxhash==1.3.0
+python-snappy==0.5.3
+tox==3.5.3
+pylint==1.9.3
+pytest-pylint==0.12.3
+pytest-mock==1.10.0
 sphinx-rtd-theme==0.2.4
-crc32c==1.2
+crc32c==1.5