pytest-benchmark: use git master code, fixes py32 issues

.travis/install.sh

@@ -43,6 +43,6 @@ fi
 
 python -m virtualenv ~/.venv
 source ~/.venv/bin/activate
-pip install -r requirements.d/travis.txt
+pip install -r requirements.d/development.txt
 pip install codecov
 pip install -e .

requirements.d/development.txt

@@ -2,5 +2,5 @@ tox
 mock
 pytest
 pytest-cov<2.0.0
-pytest-benchmark==3.0.0a4
+-e git://github.com/ionelmc/pytest-benchmark.git#egg=pytest-benchmark
 Cython

requirements.d/travis.txt

@@ -1,5 +0,0 @@
-tox
-mock
-pytest
-pytest-cov<2.0.0
-Cython