Update README.md
Create CONTRIBUTING.md
Update Identity tests to use new EF EnsureCreated method.
Forgot to save this file so it didn't get included in the last checkin.
Add builder extensions to service collection
Move extensions to Builder

Also add DbContext concrete to AddEntity extension
Move builder extensions to IdentityBuilder

Also correctly take TContext instead of looking for DbContext as a
service
Merge branch 'Ext2' into dev
Add AddIdentityEntityFramework
Rename extensions

AddEntity -> AddEntityFramework
AddSecurity -> AddHttpSignIn
Move SignInManager to Core
Fix name
Cleanup dead code
Test cleanup
Misc cleanup

Remove copy from IdentityOptions
Use DI to get Managers
Add DbContext type to IdentityBuilder AddEntity
Merge branch 'HttpSignIn' of https://github.com/aspnet/Identity into HttpSignIn

Conflicts:
	src/Microsoft.AspNet.Identity.Entity/IdentityBuilderExtensions.cs
	src/Microsoft.AspNet.Identity.Security/IdentityBuilderExtensions.cs
	test/Microsoft.AspNet.Identity.Entity.Test/SqlUserStoreTest.cs
	test/Microsoft.AspNet.Identity.Entity.Test/TestIdentityFactory.cs
	test/Microsoft.AspNet.Identity.Security.Test/HttpSignInManagerTest.cs