Fix fatal error currently breaking the build on Travis
Fix another test suite fatal error to unblock the Travis build
Add build status badge to README
Add Scrutinizer CI badge

I've had to point Scrutinizer at my own repo for now. It won't let me set up the
CI for schmittjoh/twig.js.
Remove 'range' from the list of unsupported functions
Add support for Twig's "title" filter
Add support for Twig's "trim" filter
Remove url_encode from the list of unsupported filters
Add support for Twig's "json_encode" filter
Add support for Twig's "max" function
Add support for Twig's "min" function
Remove "upper" from the list of unsupported filters
Add support for Twig's "last" filter