Add setting bundle gemfile to test_app

Author: bbonislawski

README.md

@@ -215,7 +215,7 @@ do a quick one-time creation of a test application and then you can use it to ru
 the tests.  For example, to run the tests for the core project.
 ```shell
 cd core
-bundle exec rake test_app
+BUNDLE_GEMFILE=../Gemfile bundle exec rake test_app
 bundle exec rspec spec
 ```
 

build.sh

@@ -12,7 +12,7 @@ prepare_app(){
   set_gemfile
   bundle update --quiet
   echo "Preparing test app..."
-  bundle exec rake test_app
+  BUNDLE_GEMFILE=../Gemfile bundle exec rake test_app
 }
 # Target postgres. Override with: `DB=sqlite bash build.sh`
 export DB=${DB:-postgres}