Add amplitude

- Add [Amplitude](https://amplitude.com/) ([docs](https://github.com/amplitude/Amplitude-iOS)). Implementation is pretty much one to one with ARAnalyticalProvider methods.

- The second last commit ([5b5a8d0](https://github.com/confidenceJuice/ARAnalytics/commit/5b5a8d0f44ad3aefca58122b593d75eff19e3baf)) adds some `ifdef`s, to keep the same as other providers, but are they needed since the provider wont be imported if those` ifdef`s aren't satisfied in ARAnalyticsProviders.h ?

- Bumped version.

- live tested, seems fine.