vinyl: types for v2.0.0

[thorn0]

There are 2 known issues with this version of the definitions. You can find them in the tests (search for TypeScript: known issue). Namely:

• The properties base and path are odd in that their getters and setters are of different types. TypeScript doesn't support this, so a trade-off was needed.
• Inheritance (extending File) doesn't work. Another trade-off. For the tricky type guards for the content property to work, I used subclasses with an overloaded constructor signature. The type guarding magic works, but if you try to extend File you'll get Base constructors must all have the same return type. This probably can be worked around, but so far I don't see how. Any ideas?

Please fill in this template.

• Prefer to make your PR against the types-2.0 branch.
• The package does not provide its own types, and you can not add them.
• Test the change in your own code.
• Follow the advice from the readme.
• Avoid common mistakes.

If changing an existing definition:

• Provide a URL to documentation or source code which provides context for the suggested changes: https://github.com/gulpjs/vinyl/blob/master/README.md
• Increase the version number in the header if appropriate.

[dt-bot]

vinyl/index.d.ts

to authors (@vvakame @jedmao). Could you review this PR?
👍 or 👎?

Checklist

• pass the Travis CI test?

[DenisCarriere]

Seems like this build is hung up.

https://travis-ci.org/DefinitelyTyped/DefinitelyTyped/builds/171968258

=============================================================================
                    DefinitelyTyped Test Runner 2.0.0
=============================================================================
 Typescript version: 2.1.0-dev.20161031
 Typings           : 2247
 TypeScript files  : 2247
 Total Memory      : 60387 mb
 Free Memory       : 33676 mb
 Cores             : 32
 Concurrent        : 24
============================== Syntax checking ==============================
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[thorn0]

@DenisCarriere It simply took 4822.323s for some reason. =)
I've reproduced this locally. Investigating.

[DenisCarriere]

It's strange... maybe restart manually the travis-ci build. This PR is holding up all the other PRs using the types-2.0 branch.

[thorn0]

Look at the other PRs. Same situation there. E.g. #12365: 5364.871s.
May be something with the compiler.

[thorn0]

Switching to TS v2.0.6 doesn't help. Must be something else.

[vvakame]

gulp-util/index.d.ts

to author (@jedmao). Could you review this PR?
👍 or 👎?

Checklist

• pass the Travis CI test?

[vvakame]

LGTM.