feat(*) don't execute e2e test on pull-requests

Because of security reasons, Travis won't export secure token when executing builds from pull-requests made from forks (not original repo).
This ends up not opening sauce connect tunnel, which fails the build.
This also doesn't export the Jspm registry config (which could lead to fail sometime ...)

Solution: don't run e2e tests on pull requests

* http://docs.travis-ci.com/user/pull-requests/
* #2 (comment)

.travis.yml

@@ -17,7 +17,7 @@ before_script:
 - gulp build
 - gulp clean
 - gulp build --env test
-- npm run forever-start-dist
+- '[ "${TRAVIS_PULL_REQUEST}" = "false" ] && npm run forever-start-dist || true'
 script:
 - npm test
-- npm run test-e2e
+- '[ "${TRAVIS_PULL_REQUEST}" = "false" ] && npm run test-e2e || true'