Fix ISTEXUnzip

[parmentf]

It seems that the npm package unzipper is not able to unzip that one file.

See #279.

[parmentf]

yauzl's documentation explains why no standard-compliant unzip library can use a streaming API:

Due to the design of the .zip file format, it's impossible to interpret a .zip file from start to finish (such as from a readable stream) without sacrificing correctness. The Central Directory, which is the authority on the contents of the .zip file, is at the end of a .zip file, not the beginning. A streaming API would need to either buffer the entire .zip file to get to the Central Directory before interpreting anything (defeating the purpose of a streaming interface), or rely on the Local File Headers which are interspersed through the .zip file. However, the Local File Headers are explicitly denounced in the spec as being unreliable copies of the Central Directory, so trusting them would be a violation of the spec.

Any library that offers a streaming unzip API must make one of the above two compromises, which makes the library either dishonest or nonconformant (usually the latter). This library insists on correctness and adherence to the spec, and so does not offer a streaming API.

[parmentf]

Nicolas suggested to use unzipit in place of unzipper.

Of course, this implies to use temporary files, but would fix that (rare) problem.