Rendering arrays leave a trailing comma

[aromeronavia]

Problem

When rendering an array, it renders always a trailing comma, which I'm assuming is not the intended functionality, but instead it should be rendering a comma just for all the elements prior to the last

handlebars-rust/src/json/value.rs

Lines 110 to 130 in 23ca8d7

	impl JsonRender for Json {
	fn render(&self) -> String {
	match *self {
	Json::String(ref s) => s.to_string(),
	Json::Bool(i) => i.to_string(),
	Json::Number(ref n) => n.to_string(),
	Json::Null => "".to_owned(),
	Json::Array(ref a) => {
	let mut buf = String::new();
	buf.push('[');
	for i in a.iter() {
	buf.push_str(i.render().as_ref());
	buf.push_str(", ");
	}
	buf.push(']');
	buf
	}
	Json::Object(_) => "[object]".to_owned(),
	}
	}
	}

Example

We want to render the following array: [1, 2, 3]

Expected Result

It gets rendered as [1, 2, 3]

Actual Result

It gets rendered as [1, 2, 3, ]