Fixed coding standards issue

CalculateHash return string instead of using char array param

By request from delroth, I changed the name of our Transifex
organization so it's named after the Dolphin project rather than after
him. This broke old links and the .tx/config file.

Not doing so results in the following error :

CMake Error at Externals/cubeb/CMakeLists.txt:30 (message):
  Could not find sanitizers-cmake: run

  	git submodule update --init --recursive

  in base git checkout

As the advice is correct, update readme with the correct command.

Enforce minimum supported versions of GCC and Clang

The old URL redirects to the new URL for now, but apparently it will
stop doing that in a few months. Let's update it in the Readme.

We already have a minimum required version of MSVC