Auto merge of #8867 - nfallen:6638-websocket_loader, r=jdm

Move websocket creation to resource task

This is a pull request for part of https://github.com/servo/servo/issues/6638

It includes the following changes:
-The websocket networking code (ie. making a connection, receiving data, and sending data) has been extracted out of components/script/dom/websocket.rs and into the new file components/net/websocket_loader.rs.
-websocket.rs now communicates with the resource task (components/net/resource_task.rs) to instruct it to initiate a new websocket connection
- websocket_loader.rs now provides an API sent over an IPCChannel that allows websocket.rs to receive feedback about this process and to subsequently send and receive data

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components/servo/Cargo.lock

@@ -1156,6 +1156,7 @@ dependencies = [
  "url 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.1.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "websocket 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1204,6 +1205,7 @@ dependencies = [
  "stb_image 0.2.0 (git+https://github.com/servo/rust-stb-image)",
  "url 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
+ "websocket 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]