Update jq tree version to latest, restructure dirs

* Move vendor assets into app assets
* Update jq tree version to 0.18.0
* Update JQTREE_VERSION to 0.18.0
  - did _not_ update gem version
move assets back into vendor
Merge pull request #8 from supernullset/gem-restructuring-and-update

Update jq tree version to latest, restructure dirs