Freeze requirements at their current minor versions

Except for patched versions, upgrades should be explicit.

requirements.txt

@@ -1,4 +1,24 @@
-Flask
-gunicorn
-anymarkup
-requests
+anymarkup>=0.7.0,<0.8
+anymarkup-core>=0.7.1,<0.8
+certifi>=2018.4.16
+chardet>=3.0.4,<3.1
+click==6.7
+configobj>=5.0.6,<5.1
+Flask>=1.0.2,<1.1
+Flask-WTF>=0.14.2,<0.15
+gunicorn>=19.9.0,<19.10
+idna==2.7
+itsdangerous==0.24
+Jinja2==2.10
+json5>=0.6.1,<0.7
+MarkupSafe==1.0
+mod-wsgi>=4.6.4,<4.7
+python-dateutil>=2.7.3,<2.8
+PyYAML==3.13
+requests>=2.19.1,<2.20
+six>=1.11.0,<1.12
+toml>=0.9.4,<0.10
+urllib3==1.23
+Werkzeug>=0.14.1,<0.15
+WTForms>=2.2.1,<2.3
+xmltodict>=0.11.0,<0.12