add JWT_SECRET variable to travis.yml

Author: alhoqbani

.travis.yml

@@ -7,6 +7,7 @@ php:
 env:
   global:
     - DEFAULT_COMPOSER_FLAGS="--no-interaction --no-ansi --no-progress --no-suggest"
+    - JWT_SECRET=supersecretkeyyoushouldnotcommittogithub
 
 before_script:
   - composer self-update