Bump version for release

Author: jingming

src/main/java/com/twilio/Twilio.java

@@ -12,7 +12,7 @@
  */
 public class Twilio {
 
-    public static final String VERSION = "7.1.0-alpha-1";
+    public static final String VERSION = "7.2.0-alpha-1";
     public static final String JAVA_VERSION = System.getProperty("java.version");
 
     private static String username;