Fixing bugs in DDFileLogger

Fixes for issues:

- #52 - added method `rollLogFileWithCompletion:`, `rollLogFile` became deprecated.
- #55 - when user removes log manually, it isn't actually removed, it is just moved to trash. I added `currentLogFileVnode` to monitor file descriptor, and if file gets moved or deleted - we are rolling it and create a new one.

**UPD**
Issue #129 is also fixed. Setting appropriate `NSFileProtectionKey` when creating log file on iOS.