设置pod库最低支持ios7.0

Podfile

@@ -1,5 +1,5 @@
 # Uncomment the next line to define a global platform for your project
- platform :ios, '8.0'
+ platform :ios, '7.0'
 
 target 'WSCloudStorage' do
   # Uncomment the next line if you're using Swift or would like to use dynamic frameworks