Update requirements.txt

requirements.txt

@@ -1,21 +1,21 @@
-alabaster==0.7.10
-appdirs==1.4.3
-Babel==2.4.0
-colorama==0.3.9
-docutils==0.13.1
-imagesize==0.7.1
-Jinja2==2.9.6
-MarkupSafe==1.0
-packaging==16.8
-Pygments==2.2.0
-pyparsing==2.2.0
-pytz==2017.2
-pyvmomi==6.5
-PyYAML==3.12
-requests==2.14.2
-six==1.10.0
-snowballstemmer==1.2.1
-Sphinx==1.6.1
-sphinxcontrib-websupport==1.0.1
-typing==3.6.1
-xmltodict==0.11.0
+alabaster>=0.7.10
+appdirs>=1.4.3
+Babel>=2.4.0
+colorama>=0.3.9
+docutils>=0.13.1
+imagesize>=0.7.1
+Jinja2>=2.9.6
+MarkupSafe>=1.0
+packaging>=16.8
+Pygments>=2.2.0
+pyparsing>=2.2.0
+pytz>=2017.2
+pyvmomi>=6.5
+PyYAML>=3.12
+requests>=2.14.2
+six>=1.10.0
+snowballstemmer>=1.2.1
+Sphinx>=1.6.1
+sphinxcontrib-websupport>=1.0.1
+typing>=3.6.1
+xmltodict>=0.11.0