Bump version to 0.1.8

GMRefresh.podspec

@@ -8,7 +8,7 @@
 
 Pod::Spec.new do |s|
   s.name             = "GMRefresh"
-  s.version          = "0.1.7"
+  s.version          = "0.1.8"
   s.summary          = "基于MJRefresh做的下拉刷新，自动加载更多"
   s.homepage         = "http://git.gengmei.cc/gengmeiios/GMLibrary/GMRefresh"
   s.license          = 'MIT'