Add toJSON and fromJSON methods for Graph; add it to gamestate

Still need to implement changing it in Editor, and writing tests
include graph.js in templates
Refactor adding the wall into a Gamestate method; add tests
code review fixes
Merge pull request #31 from hellochar/editor-add-obstacles

Editor add obstacles
Merge branch 'master' of https://github.com/hellochar/the_game_bazaar into user_administration