Ensure we create a new terminal instance for each new pipe.

- Prevents new session from continuing in the same terminal as an old
  one.
- This is implemented using react's key behaviour at the moment: When
  the key changes, react unmounts and remounts the component and all
  term.js stuff inside of it. Could probably do this more explicitly.

client/app/scripts/components/embedded-terminal.js

@@ -22,7 +22,7 @@ export default function EmeddedTerminal({pipe, details}) {
   // the term.js and creating a new one for the new pipe.
   return (
     <div className="terminal-embedded" style={style}>
-      <Terminal pipe={pipe} titleBarColor={titleBarColor}
+      <Terminal key={pipe.get('id')} pipe={pipe} titleBarColor={titleBarColor}
         statusBarColor={statusBarColor} containerMargin={style.right} title={title} />
     </div>
   );