Upgrade pip on osx

Signed-off-by: Daniel Nephin <dnephin@docker.com>

script/travis/ci

@@ -6,5 +6,5 @@ if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
     tox -e py27,py34 -- tests/unit
 else
     # TODO: we could also install py34 and test against it
-    python -m tox -e py27 -- tests/unit
+    tox -e py27 -- tests/unit
 fi

script/travis/install

@@ -5,5 +5,6 @@ set -ex
 if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
     pip install tox==2.1.1
 else
-    pip install --user tox==2.1.1
+    sudo pip install --upgrade pip tox==2.1.1 virtualenv
+    pip --version
 fi