Support ruby 2.4

[cben]

Bump to Webmock 2.3.1 which fixed .close stubbing for ruby 2.4.
(It's a dev dependency, shouldn't affect users of kubeclient.)

Update tests using user:pass@... urls — webmock 2.x treats basic auth as a header, not url part.
https://github.com/bblimke/webmock/blob/2.0/CHANGELOG.md#200

Fixes #242. @jrafanie please review.

[jrafanie]

LGTM @cben 👍

[moolitayer]

LGTM 👍

[moolitayer]

cc @abonas @simon3z

[abonas]

Given that the gem supports ruby starting version 2.0, how does this PR influence users that have ruby < 2.4 ? especially given the bump of webmock which looks like has a different way of handling basic auth - won't it cause regressions?

[cben]

webmock is a develoment dependency.
Other projects depending only on gem 'kubeclient' won't even get webmock installed. Projects depending on both can use whatever webmock they want:

> cat Gemfile
source 'https://rubygems.org'
gem 'kubeclient', :git => 'https://github.com/cben/kubeclient.git', :branch => 'ruby-2.4'
gem 'webmock', '= 1.0.0'

> bundle install
Fetching https://github.com/cben/kubeclient.git
Fetching gem metadata from https://rubygems.org/...........
Fetching version metadata from https://rubygems.org/.
Fetching dependency metadata from https://rubygems.org/.
Resolving dependencies...
Using public_suffix 2.0.5
Using unf_ext 0.0.7.4
Using http-form_data 1.0.1
Using http_parser.rb 0.6.0
Using recursive-open-struct 1.0.4 (was 1.0.0)
Using mime-types-data 3.2016.0521
Using netrc 0.11.0
Using bundler 1.13.1
Using addressable 2.5.1
Using unf 0.1.4
Using mime-types 3.1
Installing webmock 1.0.0
Using domain_name 0.5.20170404
Using http-cookie 1.0.3
Using http 2.2.2 (was 0.9.8)
Using rest-client 2.0.2
Using kubeclient 2.3.0 from https://github.com/cben/kubeclient.git (at ruby-2.4@1065d39)
Bundle complete! 2 Gemfile dependencies, 17 gems now installed.
Use `bundle show [gemname]` to see where a bundled gem is installed.

[jrafanie]

Given that the gem supports ruby starting version 2.0, how does this PR influence users that have ruby < 2.4 ? especially given the bump of webmock which looks like has a different way of handling basic auth - won't it cause regressions?

@abonas In addition to what @cben mentioned about using kubeclient in a project already using an older webmock, the tests should pick up regressions since we now test 2.0 through 2.4.