Update .travis.yml

Author: ConfZ

.travis.yml

@@ -3,5 +3,7 @@
     - "3.6"
   script:
     - pytest
+  install:
+    - pip install -r requirements.txt
   after_success:
     - bash <(curl -s https://blackducksoftware.github.io/hub-detect/hub-detect.sh) --blackduck.hub.url="https://hubeval32.blackducksoftware.com" --blackduck.hub.username="ntu" --blackduck.hub.password="ntu@2018" --blackduck.hub.trust.cert=true --detect.policy.check=true