Android Lollipop needs WRITE_EXTERNAL_STORAGE but it shouldn't.

[murraycu]

Android Lollipop throws IOExceptions when reading or writing from the getExternalFilesCacheDir() directory unless we request WRITE_EXTERNAL_STORAGE permission (and READ_EXTERNAL_STORAGE, which is then implicitly requested). But that shouldn't be necessary since API 18:
http://developer.android.com/reference/android/Manifest.permission.html#WRITE_EXTERNAL_STORAGE

This commit requests the permission, but it shouldn't be necessary:
75aa986

I asked this on StackExchange too:
http://stackoverflow.com/questions/27016647/why-do-i-need-the-write-external-storage-permission-with-getexternalcachedir-o?sgp=2