Fixes issue jeresig#124 JSON is overwritten if unable to parse the fi…

…le in DEV mode.

If JSON file exists and in DEV mode but the locale is undefined - HALTS ALL execution with an expection to prevent the files from being overwritten.

i18n.js

@@ -330,6 +330,10 @@ i18n.prototype = {
 
 			locale = this.defaultLocale;
 
+			if ((this.devMode) && (fs.existsSync(this.locateFile(locale)))) {
+				throw new Error('Please correct potential parse errors in i18n JSON file ' + this.locateFile(locale));
+			}
+
 			this.initLocale(locale, {});
 		}