Bump version to 1.2.4

GMBase.podspec

 Pod::Spec.new do |s|
     s.name             = 'GMBase'
-    s.version          = '1.2.3'
+    s.version          = '1.2.4'
     s.summary          = '更美iOS APP 的 Objective-C 基础Pod库'
     s.homepage         = 'http://git.wanmeizhensuo.com/gengmeiios/GMBase'
     s.license          = '仅限北京更美互动信息科技有限公司内部使用'