Improve post composer + replying

- Make it modular so that different entry points can show different
things and respond differently (reply, new discussion, edit post)
- Resizable
- Fullscreen
- Confirm on close

ember/app/components/discussions/composer-reply.js

@@ -0,0 +1,43 @@
+import Ember from 'ember';
+
+import TaggedArray from '../../utils/tagged-array';
+
+var precompileTemplate = Ember.Handlebars.compile;
+
+export default Ember.Component.extend(Ember.Evented, {
+	layoutName: 'components/discussions/composer-body',
+
+	placeholder: 'Write your reply...',
+	submitLabel: 'Post Reply',
+	value: '',
+
+	didInsertElement: function() {
+		var headerItems = TaggedArray.create();
+		this.trigger('populateHeader', headerItems);
+		this.set('headerItems', headerItems);
+	},
+
+	populateHeader: function(header) {
+		var title = Ember.Component.create({
+			tagName: 'h3',
+			layout: precompileTemplate('Replying to <em>{{component.discussion.title}}</em>'),
+			component: this
+		});
+		header.pushObjectWithTag(title, 'title');
+	},
+
+	actions: {
+		submit: function(value) {
+			this.get('submit').call(this, value);
+		},
+		willExit: function(abort) {
+			if (this.get('value') && ! confirm('You have not posted your reply. Do you wish to discard it?')) {
+				abort();
+			}
+		},
+		reset: function() {
+			this.set('loading', false);
+			this.set('value', '');
+		},
+	}
+});