Instead of `#import "CodePush.h"`, use `#import "<CodePush/CodePush.h>` and export CodePush.h from our module.
* [iOS][Build] Add `Headers` and `Copy Files` build phases
Due to changes in new release of `react-native@0.40.0`
there is `CodePush.h file not found` error occures.
To fix it I've added `CodePush.h` header file in `Headers`
and `Copy Files` build phases and changed
`codePushHeaderImportStatement` variable value from `#import "CodePush.h"`
to `#import <CodePush/CodePush.h>` in `postlink.js` file.
Fix https://github.com/Microsoft/react-native-code-push/issues/662
* readme: update iOS manual plugin installation/usage documentation
Due to changes in React Native v0.40.0 and changes in CodePush project Step 6. of iOS manual plugin installation (add “Header Search Paths”) is not needed anymore. Also changed path to `CodePush.h` file in `AppDelegate.m` to `#import <CodePush/CodePush.h>`
