ci: update .travis.yml (#37)

Update travis configuration for auto deployment of pull requests to
gh-pages.

Fixes #4

.travis.yml

@@ -11,7 +11,13 @@ before_script:
 
 script:
   - ng lint
-  - ng build --prod
-
-after_success:
+  - ng build --prod --base-href="/web-app/"
 
+deploy:
+  provider: pages
+  skip-cleanup: true
+  local-dir: dist/web-app
+  github-token: $GITHUB_TOKEN
+  keep-history: true
+  on:
+    branch: master