Make HTTP method match as case-insensitive

[rynowak]

I know the spec says that HTTP methods are case-sensitive - but don't we do this other places?

https://github.com/aspnet/CORS/blob/dev/src/Microsoft.AspNetCore.Cors/Infrastructure/CorsMiddleware.cs#L103

[rynowak]

/cc @Tratcher

[davidfowl]

We should not, we should be case insensitive where we can.

[rynowak]

We should not, we should be case insensitive where we can.

Error CS1092: Statement ambiguous

[davidfowl]

I misread the link, we should be case insensitive and fix this code 😄

[rynowak]

Are you saying we should change the other stuff?

[davidfowl]

It should be case insensitive across the board

[Tratcher]

Agreed, case insensitive.

[Eilon]

@Tratcher are there other areas where we are not case-sensitive, but should be?

[Eilon]

Moving to post-RTM.