Log chef-zero instead of chef-solo
docs/getting-started: install the _latest_ version

See #5082
Merge pull request #5077 from mitchellh/sethvargo/zero_log

Log chef-zero instead of chef-solo
Revert "Doc: Fix double underscore rsync attribute documentation"
Merge pull request #5087 from mitchellh/revert-5031-patch-4

Revert "Doc: Fix double underscore rsync attribute documentation"
FIX [mitchellh/vagrant#4889] .curlrc ignored

- change "-q" to "--no-progress-bar" in downloader.rb
- update requisite tests

The initial fix for mitchellh/vagrant#4494 created a regression by causing curlrc to be completely ignored. By ignoring curlrc, significant curl functionality, such as proxy use, configuration of CA certs, and out-of-source password storage (via netrc), was made difficult or impossible.

This repair, suggested by @slicen, more narrowly repairs the original issue (mitchellh/vagrant#4494) and still allows for the use of curlrc configuration directives.

[1] mitchellh/vagrant#4889
[2] mitchellh/vagrant#4494