Delete "tmp" directory after successful gem installation.

[flavorjones]

See this StackOverflow question for the use case around deleting the tmp directory in Nokogiri 1.6.0+.

[knu]

Please review the static_clean branch.
https://github.com/sparklemotion/nokogiri/tree/static_clean

[virgilm]

Any plans on integrating this patch?

[knu]

@virgilm I don't know. I see only few people showed an interest in it. I need a real test report and a review before it can be merged.

[benlangfeld]

@knu How do we use your patch? It looks like it's not set as the default behaviour and the --clean option needs passing, but where? I feel strongly that this should be the default behaviour :)

[knu]

It is enabled by default.

[knu]

Looks like @flavorjones has been busy, so I'll take this.

[knu]

See #952.