Allow limiting the download size via CURL progress callback

[julik]

I thought we could expand on the interrupt handling and add a download size limiter. The rationale is simple: sometimes you want to make sure the server on the other end will not overflow your disk (by mistake or by malice).

Note that I had to switch to Ubuntu 14 on Travis because on their Precise stuff libCURL has a bug that won't let it stop on an interrupt. Same for Session#interrupt but there were no tests for that either, so got to add them soon.

[toland]

I am +1 on the change, but one of the specs fails on Travis. Fix the failing spec and I am good with merging.

Thanks!

[julik]

👍 will do

[julik]

@toland 🎉

[toland]

LGTM