Added layer comments via 'metadata.maputnik:comment' (issue #28)

src/components/inputs/StringInput.jsx

@@ -20,16 +20,33 @@ class StringInput extends React.Component {
   }
 
   render() {
-    return <input
-      className="maputnik-string"
-      style={this.props.style}
-      value={this.state.value}
-      placeholder={this.props.default}
-      onChange={e => this.setState({ value: e.target.value })}
-      onBlur={() => {
+    let tag;
+    let classes;
+
+    if(!!this.props.multi) {
+      tag = "textarea"
+      classes = [
+        "maputnik-string",
+        "maputnik-string--multi"
+      ]
+    }
+    else {
+      tag = "input"
+      classes = [
+        "maputnik-string"
+      ]
+    }
+
+    return React.createElement(tag, {
+      className: classes.join(" "),
+      style: this.props.style,
+      value: this.state.value,
+      placeholder: this.props.default,
+      onChange: e => this.setState({ value: e.target.value }),
+      onBlur: () => {
         if(this.state.value!==this.props.value) this.props.onChange(this.state.value)
-      }}
-    />
+      }
+    });
   }
 }