* Replacing FIR_SWIFT_NAME macro with NS_SWIFT_NAME.
This pushes the minimum Xcode version to 7.3, as NS_SWIFT_NAME was
limited before that version (which is why the macro was introduced in
the first place).
* Fixed FIRMessaging header
* Update Auth version to 4.3.0
* Revert "Removes user meta from public API (#308)"
This reverts commit 1602391bf8.
* Revert "Removes metadata from swift sample (#318)"
This reverts commit 804ff523a2.