Add a "container" option instead of using $('body')

Allow usage of another container that the cached version of body (moreover that can change with some SPA)
Allow DOM selector in container option and add tests
Merge branch 'patch-1' of git://github.com/sroze/bootbox into sroze-patch-1

Conflicts:
	tests/defaults.test.js
[GH-147] tweak container tests a little
Wrap bootbox as an UMD module
[GH-186] add UMD globals to jshint config
[GH-186] make init method return an object rather than assigning it to window; update tests
Merge branch 'jochenberger-umd-module'
Merge remote-tracking branch 'upstream/master'