Support war file (Java web package)

[nianjiang]

Introduce the format you are requesting.

war file, is the type of java web package.
Naturally， it is same with zip, using zip function can Unarchive the war file.

What do YOU use this format for?

What is the format's conventional file extension(s)?

Please link to the format's formal or official specification(s).

Which Go libraries could be used to implement this format?

[JalonSolov]

This would "just work" if ByHeader support were added to more formats. All zip files would be handled as zip files, regardless of file extension. Truthfully, ByHeader should always be the default, since file extensions are wrong far too often.

[mholt]

If it is in fact same as zip, then @JalonSolov is right, and this is now implemented in #302, which will become v4 of this package.