Check for PhantomJS installed in script/bootstrap

Author: mislav

script/bootstrap

@@ -2,3 +2,10 @@
 set -e
 
 bundle install
+
+if phantom_version="$(phantomjs --version)"; then
+  echo "PhantomJS $phantom_version"
+else
+  echo "Warning: script/test will not be able to run, but you can still start" >&2
+  echo "script/server and open the test suite in your browser." >&2
+fi