Bump pyyaml from 3.11 to 5.1

dev-requirements.txt

@@ -4,43 +4,35 @@
 #
 #    pip-compile --output-file dev-requirements.txt dev-requirements.in
 #
-
 alabaster==0.7.8          # via sphinx
 argh==0.26.2              # via watchdog
 babel==2.3.4              # via sphinx
 bumpversion==0.5.3
+check-manifest==0.39
 click==6.6                # via pip-tools
 coverage==4.1
 docutils==0.12            # via sphinx
 first==2.0.1              # via pip-tools
 flake8==2.5.4
 imagesize==0.7.1          # via sphinx
-Jinja2==2.8               # via sphinx
-MarkupSafe==0.23          # via jinja2
+jinja2==2.8               # via sphinx
+markupsafe==0.23          # via jinja2
 mccabe==0.4.0             # via flake8
 pathtools==0.1.2          # via watchdog
 pep8==1.7.0               # via flake8
 pip-tools==1.6.5
-pkginfo==1.2.1            # via twine
 pluggy==0.3.1             # via tox
 py==1.4.31                # via pytest, tox
-pycparser==2.14           # via cffi
 pyflakes==1.0.0           # via flake8
-Pygments==2.1.3           # via sphinx
+pygments==2.1.3           # via sphinx
+pytest==2.9.1
 pytz==2016.4              # via babel
-PyYAML==3.11              # via watchdog
-requests-toolbelt==0.6.2  # via twine
-requests==2.10.0          # via requests-toolbelt, twine
-six==1.10.0               # via cryptography, pip-tools, sphinx
+pyyaml==5.1               # via watchdog
+six==1.10.0               # via pip-tools, sphinx
 snowballstemmer==1.2.1    # via sphinx
-Sphinx==1.4.1
+sphinx==1.4.1
+toml==0.10.0              # via check-manifest
 tox==2.3.1
-twine==1.6.5
 virtualenv==15.0.1        # via tox
 watchdog==0.8.3
 wheel==0.29.0
-pytest==2.9.1
-
-# The following packages are commented out because they are
-# considered to be unsafe in a requirements file:
-# setuptools                # via cryptography, twine