improve checks in stream? for http1

[zarqman]

This PR tightens up the check in stream? for HTTP/1.1 requests by ensuring the sec-websocket-accept header was verified in addition to status == 101.

Before

Status not 101       : `stream?` => false
101 w/missing header : `stream?` => true
Bad header           : raises exception

After

Status not 101       : `stream?` => false
101 w/missing header : `stream?` => false
Bad header           : raises exception

Reference

RFC 6455, near the end of section 4.1, says that a WS connection must be failed if the header is missing or invalid (in point (4), at the bottom of page 19).

Types of Changes

• Bug fix.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[ioquatix]

Thanks, this is a great addition.