diff --git a/.travis.yml b/.travis.yml
index 442264ab..eeb21d97 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@
 language: python
 sudo: false
 cache:
+  # See http://docs.travis-ci.com/user/caching/#pip-cache
   directories:
     - $HOME/.cache/pip
 addons:
@@ -28,14 +29,13 @@ notifications:
     on_start: false     # default: false
 
 python:
-- 2.6
-- 2.7
-- 3.2
-- 3.3
-- 3.4
+  - 2.6
+  - 2.7
+  - 3.2
+  - 3.3
+  - 3.4
 
 before_install:
-    - sudo apt-get update; true
     - source tools/travis_before_install.sh
 
     - which python; python --version
@@ -43,8 +43,7 @@ before_install:
     - tools/build_versions.py
 
 install:
-    - python setup.py build_ext --inplace
-    - python setup.py install
+    - python setup.py develop
 
 script: tools/travis_script.sh
 
diff --git a/optional_requirements.txt b/optional_requirements.txt
new file mode 100644
index 00000000..fe6503c5
--- /dev/null
+++ b/optional_requirements.txt
@@ -0,0 +1,5 @@
+PySide; python_version != '2.7'
+imread; python_version != '2.7' and python_version != '3.2'
+SimpleITK; python_version != '3.2' and python_version != '3.4'
+astropy
+tifffile
diff --git a/tools/travis_before_install.sh b/tools/travis_before_install.sh
index fce0a367..09f67451 100755
--- a/tools/travis_before_install.sh
+++ b/tools/travis_before_install.sh
@@ -49,7 +49,8 @@ fi
 virtualenv -p python ~/venv
 source ~/venv/bin/activate
 
-retry pip install -q wheel flake8 coveralls nose
+pip install --upgrade pip
+pip install --retries 3 -q wheel flake8 coveralls nose
 
 # on Python 3.2, use matplotlib 1.3.1
 if [[ $TRAVIS_PYTHON_VERSION == 3.2 ]]; then
@@ -60,10 +61,12 @@ fi
 for requirement in $WHEELBINARIES; do
     WHEELS="$WHEELS $(grep $requirement requirements.txt)"
 done
-retry pip install -q $WHEELHOUSE $WHEELS
+pip install --retries 3 -q $WHEELHOUSE $WHEELS
 
-retry pip install -q -r requirements.txt
+pip install --retries 3 -q -r requirements.txt
 
+# Show what's installed
+pip list
 
 section () {
     echo -en "travis_fold:start:$1\r"
diff --git a/tools/travis_notes.txt b/tools/travis_notes.txt
index 84271821..0b18aeb1 100644
--- a/tools/travis_notes.txt
+++ b/tools/travis_notes.txt
@@ -14,8 +14,9 @@ the yaml file is valid.
      set -ex
    ```
 
-- Use the `retry` bash function from `before_install.sh` before a command to have it try 3 times before
-failing (useful for installing from third party sources).
+- Use the `retry` bash function from `before_install.sh` before a command to
+have it try 3 times before failing.
+- Use `pip install --retries N` for retrying package downloads.
 - Use the `section` function to start a folded section of the script.
 Section names must have underscores or dots instead of spaces and must be
 accompanied by a corresponding `section_end` call.
diff --git a/tools/travis_script.sh b/tools/travis_script.sh
index 3c459ac7..efa3071e 100755
--- a/tools/travis_script.sh
+++ b/tools/travis_script.sh
@@ -20,6 +20,9 @@ section_end "Flake8.test"
 
 section "Install.optional.dependencies"
 
+# Install most of the optional packages
+pip install --retries 3 -q -r ./optional_requirements.txt $WHEELHOUSE
+
 # Install Qt and then update the Matplotlib settings
 if [[ $PY == 2.7* ]]; then
     # http://stackoverflow.com/a/9716100
@@ -37,29 +40,15 @@ if [[ $PY == 2.7* ]]; then
     done
 
 else
-    retry pip install -q PySide $WHEELHOUSE
     python ~/venv/bin/pyside_postinstall.py -install
-fi 
-
-# Install imread from wheelhouse if available (not 3.2)
-if [[ $PY != 3.2 ]]; then
-    retry pip install -q $WHEELHOUSE
 fi
 
-# Install SimpleITK from wheelhouse if available (not 3.2 or 3.4)
-if [[ $PY =~ 3\.[24] ]]; then
-    echo "SimpleITK unavailable on $PY"
-else
-    retry pip install -q SimpleITK $WHEELHOUSE
-fi
-
-retry pip install -q astropy $WHEELHOUSE
-
 if [[ $PY == 2.* ]]; then
-    retry pip install -q pyamg
+    pip install --retries 3 -q pyamg
 fi
 
-retry pip install -q tifffile
+# Show what's installed
+pip list
 
 section_end "Install.optional.dependencies"