Refine wording of README about delegation to other bodies

This slightly rewords the README to make two points:

• GHC HQ has overall authority over GHC, and delegates that authority to the GHC Steering Committee and the CLC.
• Major language features are expected to go to the GHC Steering Committee.

README.mkd

@@ -79,8 +79,8 @@ As an open-source project, *decisions about GHC are primarily taken by consensus
 
 The GHC HQ group is very much a back-stop if all else fails; almost everything gets done by the team.
 
-Note that this only applies to the GHC project and its implementation:
-* Decisions about the language that GHC compiles fall in the remit of the [GHC Steering Committee](https://github.com/ghc-proposals/ghc-proposals).
+The GHC HQ group delegates authority to various other bodies:
+* Decisions about major features and the language that GHC compiles fall in the remit of the [GHC Steering Committee](https://github.com/ghc-proposals/ghc-proposals).
 * Decisions about GHC’s core library design are the territory of the [Core Libraries Committee](https://github.com/haskell/core-libraries-committee).
 
 ### 3.1 What sort of decisions does the GHC HQ group take?