Simple type-checking in dev-mode

Displays the warning in console if the type of the new value of data property isn't equal to previous. Important in development when interfaces of components are still too fluid.

src/shared/index.js

@@ -140,6 +140,14 @@ export function setDev(newState) {
 	}
 
 	this._checkReadOnly(newState);
+	
+	Object.keys(newState).forEach(prop => {
+		if (prop in this._state && typeof this._state[prop] !== 'undefined' 
+			&& typeof this._state[prop] !== typeof newState[prop]) {
+			console.warn('Type of data property "' + prop + '" not match with previous one.');
+		}
+	});
+	
 	set.call(this, newState);
 }