Added pip-tools for requirement manageing

Updated requirements

.travis.yml

@@ -31,6 +31,6 @@ script:
   - isort --check-only --recursive --diff .
   - flake8 --jobs=2 .
   - pep257 django_select2
-  - coverage run --source=django_select2 runtests.py
+  - coverage run --source=django_select2 py.test
 after_success:
   - coveralls

requirements_dev.in

@@ -0,0 +1,10 @@
+django-appconf
+flake8
+pep8-naming
+mccabe
+isort
+pep257
+pytest
+pytest-django
+selenium
+model-mommy

requirements_dev.txt

@@ -1,19 +1,23 @@
--e .
+#
+# This file is autogenerated by pip-compile
+# Make changes in requirements_dev.in, then run this to update:
+#
+#    pip-compile requirements_dev.in
+#
 django-appconf==1.0.1
-django==1.8.4             # via model-mommy
-flake8==2.4.1
+django==1.8.7             # via model-mommy
+flake8==2.5.0
 isort==4.2.2
-mccabe==0.3.1             # via flake8
+mccabe==0.3.1
 mock==1.3.0               # via model-mommy
-model-mommy==1.2.5
-pbr==1.8.0                # via mock
-pep257==0.5.0
+model-mommy==1.2.5.1
+pbr==1.8.1                # via mock
+pep257==0.7.0
 pep8-naming==0.3.3
 pep8==1.5.7               # via flake8
-py==1.4.30                # via pytest
-pyflakes==0.8.1           # via flake8
-pytest-django==2.8.0
-pytest==2.7.2
-requests==2.7.0
-selenium==2.46.0
-six==1.9.0                # via django-appconf, mock, model-mommy
+py==1.4.31                # via pytest
+pyflakes==1.0.0           # via flake8
+pytest-django==2.9.1
+pytest==2.8.3
+selenium==2.48.0
+six==1.10.0               # via django-appconf, mock, model-mommy