fix error: Do not hide the loading view when collection.length === 0

example:

new bbGrid.View({
	collection: new Backbone.Collection([]),
	...
});
fix error: Do not select the selected rows when set selectedRows values, and set multiselect to true

example:
new bbGrid.View({
	container: $('#bbGrid-clear'),
	collection: new Backbone.Collection([
		{id: 1, name: 'wenzhixin', company: 'scutech', email: 'wenzhixin2010@gmail.com'}
	]),
	selectedRows: [1],
	multiselect: true,
	colModel: [
		{ title: 'ID', name: 'id' },
		{ title: 'Full Name', name: 'name'},
		{ title: 'Company', name: 'company'},
		{ title: 'Email', name: 'email' }
	]
});
Merge pull request #16 from wenzhixin/master

fix error