Fix #100 - Add "back" button to certain views

Also fix reloading of timelines after merge-type events

app/assets/javascripts/components/components/column_back_button.jsx

@@ -0,0 +1,40 @@
+import PureRenderMixin from 'react-addons-pure-render-mixin';
+
+const outerStyle = {
+  padding: '15px',
+  fontSize: '16px',
+  background: '#2f3441',
+  flex: '0 0 auto',
+  cursor: 'pointer',
+  color: '#2b90d9'
+};
+
+const iconStyle = {
+  display: 'inline-block',
+  marginRight: '5px'
+};
+
+const ColumnBackButton = React.createClass({
+
+  contextTypes: {
+    router: React.PropTypes.object
+  },
+
+  mixins: [PureRenderMixin],
+
+  handleClick () {
+    this.context.router.goBack();
+  },
+
+  render () {
+    return (
+      <div onClick={this.handleClick} style={outerStyle}>
+        <i className='fa fa-fw fa-chevron-left' style={iconStyle} />
+        Back
+      </div>
+    );
+  }
+
+});
+
+export default ColumnBackButton;