Merge pull request #785 from ofek/patch-1

upgrade pip in Travis too

Author: joeykrug

.travis.yml

@@ -23,7 +23,7 @@ before_install:
   - if [ -n "$SOLC_VERSION" ]; then sudo apt-get install -y tree unzip; fi
 install:
   - if [ -n "$SOLC_VERSION" ]; then /.$TRAVIS_BUILD_DIR/.travis/install_solc.sh; fi
-  - travis_retry pip install setuptools --upgrade
+  - travis_retry pip install pip setuptools --upgrade
   - travis_retry pip install tox
   - travis_retry pip install coverage
   - travis_retry pip install flake8