[fix] Use `derequire` in our build tool for the Engine.IO client

Fixes #226
[minor] Rebuild the Engine.IO client -- version 1.2.1
[doc] Statement is no longer true
[minor] throw for Socket.IO 1.0
[minor] Use Primus error
[fix] Merge pusher's sockjs patches, fixes #245
[doc] Start on migration guides
[minor] Improved thrown error wording
[dist] 2.2.3
[fix] Engine
[dist] 2.2.4
[minor] Consistency
small typo fix
Merge pull request #248 from seanewest/typo-fix

small typo fix
[minor] Fix a typo and the URL of the Engine.IO client repo
[patch] Add a patch for the Engine.IO client to make it work again when using RequireJS

Fixes #249