Allow stream_channel version 2.x (flutter#18)

Although there are no imports to `stream_channel` from this package we
do use some of the APIs. None of those apis are impacted by the planned
breaking changes in `stream_channel`.

- Extend range for `stream_channel`.
- Correct style on other constraints.
- Expand description.

Author: natebosch

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.2.2+5
+
+* Allow `stream_channel` version 2.x
+
 ## 0.2.2+4
 
 * Fix the check for `onConnection` to check the number of arguments  and not

pubspec.yaml

@@ -1,18 +1,19 @@
 name: shelf_web_socket
-version: 0.2.2+4
+version: 0.2.2+5
 
-description: A WebSocket handler for Shelf.
+description: >-
+  A shelf handler that wires up a listener for every connection.
 author: Dart Team <[email protected]>
-homepage: http://github.com/dart-lang/shelf_web_socket
+homepage: https://github.com/dart-lang/shelf_web_socket
 
 environment:
-  sdk: '>=2.0.0-dev.17.0 <3.0.0'
+  sdk: ">=2.0.0 <3.0.0"
 
 dependencies:
-  shelf: '>=0.7.0 <0.8.0'
-  stream_channel: ^1.4.0
+  shelf: ^0.7.0
   web_socket_channel: ^1.0.0
+  stream_channel: ">1.4.0 <3.0.0"
 
 dev_dependencies:
-  http: '>=0.10.0 <0.12.0'
-  test: '>=0.12.42 <2.0.0'
+  http: ">=0.10.0 <0.12.0"
+  test: ^1.0.0