Support TypeScript 2.5

[azz]

https://blogs.msdn.microsoft.com/typescript/2017/08/17/announcing-typescript-2-5-rc/

• Optional Catch Binding

[JamesHenry]

Anyone wishing to use 2.5 before it is the stable release can install the latest git commit from this PR: #370

[azz]

https://blogs.msdn.microsoft.com/typescript/2017/08/31/announcing-typescript-2-5/

[donaldpipowitch]

I couldn't found any errors with 2.5 so far 👍