Add a selectable option to nodes so that some can be selected and others can serve as expansion click targets.
Update README.md

example json was invalid
Merge pull request #13 from maldoinc/patch-1

Update README.md
Merge branch 'selectable-node-config' of https://github.com/tbaron/bootstrap-treeview
Merge branch 'master' of https://github.com/jonmiles/bootstrap-treeview into dev

Conflicts:
	tests/tests.js