Fix install settings for Travis (#3)

This change fixes the .travis.yml file to work properly. The one committed initially fails to properly install _pine itself as well as the requirements.

.travis.yml

@@ -2,7 +2,10 @@ language: python
 python:
   - "3.7-dev" # 3.7 development branch
 # command to install dependencies
-install: "pip install -r test-requirements.txt"
+install:
+  - pip install .
+  - pip install -r requirements.txt
+  - pip install -r test-requirements.txt
 # command to run tests
 script: python -m unittest discover -v tests
 #after_success: