Tag WebSockets.jl v0.4.0

[attobot]

Repository: JuliaWeb/WebSockets.jl
Release: v0.4.0
Travis:
Diff: vs v0.3.0
requires vs v0.3.0:

--- 0.3.0/requires
+++ 0.4.0/requires
@@ -1,6 +1,6 @@
-julia 0.4
-Compat 0.9.5
-HttpCommon 0.0.3
-HttpServer 0.0.4
+julia 0.5
+Compat 0.28.0
+HttpCommon
+HttpServer
 Codecs
 MbedTLS

cc: @aviks

Please make sure that:

• CI passes for supported Julia versions (if applicable).
• Version bounds reflect minimum requirements.

[aviks]

cc @hustf

Attobot hadn't created a PR for v0.4.0. I retagged it in the repo, and this PR is the result.