fixed wrong url path to icons sprite

one url() call to the sprite img was wrong. fixed it like the other paths.
Merge pull request #31 from piffie/patch-1

fixed wrong url path to icons sprite
Correct options.history assignment when options.enabledHistory used.
Merge branch 'hotfix/1.7.0.1' into develop

Conflicts:
	jsoneditor/jsoneditor.css
	jsoneditor/jsoneditor.js