Use most recent sphinx versions

Author: Chilipp

.travis.yml

@@ -1,22 +1,15 @@
 language: python
 python:
-  # We don't actually use the Travis Python, but this keeps it organized.
   - "2.7"
-  - "3.4"
   - "3.5"
+  - "3.6"
 env:
-  - SPHINX_VERSION=1.3.1
-  - SPHINX_VERSION=1.3.2
-  - SPHINX_VERSION=1.3.3
-  - SPHINX_VERSION=1.3.4
-  - SPHINX_VERSION=1.3.5
   - SPHINX_VERSION=1.3.6
-  - SPHINX_VERSION=1.4.1
-  - SPHINX_VERSION=1.4.2
-  - SPHINX_VERSION=1.4.3
-  - SPHINX_VERSION=1.4.4
-  - SPHINX_VERSION=1.4.5
   - SPHINX_VERSION=1.4.6
+  - SPHINX_VERSION=1.5.6
+  - SPHINX_VERSION=1.6.1
+  - SPHINX_VERSION=1.6.2
+  - SPHINX_VERSION=1.6.3
 install:
   - pip install coveralls
   - pip install sphinx==${SPHINX_VERSION}