Update/clean up dependencies on Travis

.travis.yml

@@ -6,15 +6,6 @@ python:
 # Setting sudo to false opts in to Travis-CI container-based builds.
 sudo: false
 
-# The apt packages below are needed for sphinx builds, which can no longer
-# be installed with sudo apt-get.
-addons:
-    apt:
-        packages:
-            - graphviz
-            - texlive-latex-extra
-            - dvipng
-
 env:
     global:
         # The following versions are the 'default' for tests, unless
@@ -23,8 +14,8 @@ env:
         - NUMPY_VERSION=stable
         - ASTROPY_VERSION=stable
         - SETUP_CMD='test'
-        - PIP_DEPENDENCIES='git+https://github.com/spacetelescope/poppy.git#egg=poppy jwxml git+https://github.com/spacetelescope/pysiaf.git#egg=pysiaf nbsphinx Sphinx==1.5.6 git+https://github.com/astropy/photutils.git#egg=phoutils'
-        - CONDA_DEPENDENCIES='scipy matplotlib six cython'
+        - PIP_DEPENDENCIES='git+https://github.com/spacetelescope/poppy.git#egg=poppy jwxml git+https://github.com/spacetelescope/pysiaf.git#egg=pysiaf'
+        - CONDA_DEPENDENCIES='scipy matplotlib cython'
 
         # For headless testing of code that imports PyPlot:
         - MPLBACKEND=Agg
@@ -44,8 +35,8 @@ matrix:
         # Check for Sphinx doc build errors
         - python: 3.6
           env: SETUP_CMD='build_sphinx'
-                CONDA_DEPENDENCIES='scipy matplotlib six cython nbsphinx pandoc'
-                PIP_DEPENDENCIES='git+https://github.com/spacetelescope/poppy.git#egg=poppy jwxml git+https://github.com/spacetelescope/pysiaf.git#egg=pysiaf nbsphinx Sphinx==1.5.6 git+https://github.com/astropy/photutils.git#egg=phoutils sphinx_rtd_theme stsci_rtd_theme sphinx-automodapi'
+                CONDA_DEPENDENCIES='scipy matplotlib cython nbsphinx pandoc'
+                PIP_DEPENDENCIES='git+https://github.com/spacetelescope/poppy.git#egg=poppy jwxml git+https://github.com/spacetelescope/pysiaf.git#egg=pysiaf nbsphinx sphinx_rtd_theme stsci_rtd_theme sphinx-automodapi'
 
         # Try Astropy development version
         - python: 3.6