Add required tvOS version to README.
Add required tvOS version to README.

Swinject/Swinject,yoichitgy/Swinject,yoichitgy/Swinject,yoichitgy/Swinject,Swinject/Swinject,Swinject/Swinject,Swinject/Swinject,yoichitgy/Swinject