Update min platform (#13)

This matches what React supports, and allows building this as a framework

See: https://github.com/facebook/react-native/blob/master/React.podspec#L39

Author: ajohnsonRH

boost-for-react-native.podspec

@@ -10,7 +10,7 @@ Pod::Spec.new do |spec|
   spec.compiler_flags = '-Wno-documentation'
 
   # Pinning to the same version as React.podspec.
-  spec.platforms = { :ios => '8.0', :tvos => '9.2' }
+  spec.platforms = { :ios => '10.0', :tvos => '10.0' }
   spec.requires_arc = false
 
   spec.module_name = 'boost'