Add valid_url? helper

[markets]

Closes #158

Add new helper valid_url? to check if a url is valid in some of the enabled providers:

> VideoInfo.valid_url?('http://www.youtube.com/watch?v=AT_5xOGh6Ko')
=> true
> VideoInfo.valid_url?('http://vimeo.com/898029')
=> true
> VideoInfo.valid_url?('http://www.example.com/video/12345')
=> false

[houndci-bot]

Some files could not be reviewed due to errors:

.rubocop.yml: Style/DotPosition has the wrong namespace - should be Layout

.rubocop.yml: Style/DotPosition has the wrong namespace - should be Layout
.rubocop.yml: Style/FileName has the wrong namespace - should be Naming
.rubocop.yml: Style/PredicateName has the wrong namespace - should be Naming
.rubocop.yml: Style/AccessorMethodName has the wrong namespace - should be Naming
Error: The `Style/TrailingCommaInLiteral` cop no longer exists. Please use `Style/TrailingCommaInArrayLiteral` and/or `Style/TrailingCommaInHashLiteral` instead.
(obsolete configuration found in .rubocop.yml, please update it)
obsolete parameter MaxLineLength (for Style/IfUnlessModifier) found in .rubocop.yml
`Style/IfUnlessModifier: MaxLineLength` has been removed. Use `Metrics/LineLength: Max` instead

[houndci-bot]

Some files could not be reviewed due to errors:

.rubocop.yml: Style/DotPosition has the wrong namespace - should be Layout

.rubocop.yml: Style/DotPosition has the wrong namespace - should be Layout
.rubocop.yml: Style/FileName has the wrong namespace - should be Naming
.rubocop.yml: Style/PredicateName has the wrong namespace - should be Naming
.rubocop.yml: Style/AccessorMethodName has the wrong namespace - should be Naming
Error: The `Style/TrailingCommaInLiteral` cop no longer exists. Please use `Style/TrailingCommaInArrayLiteral` and/or `Style/TrailingCommaInHashLiteral` instead.
(obsolete configuration found in .rubocop.yml, please update it)
obsolete parameter MaxLineLength (for Style/IfUnlessModifier) found in .rubocop.yml
`Style/IfUnlessModifier: MaxLineLength` has been removed. Use `Metrics/LineLength: Max` instead

[markets]

@thibaudgg updated with your suggestions + mention in the README.

NOTE the build seems a bit broken, over 40 specs fail (mostly related to vcr) for me locally (also in CI). But this one passes ✔️ without any problem:

$ bundle exec rspec spec/lib/video_info_spec.rb 
...
Finished in 0.01914 seconds (files took 0.67107 seconds to load)
10 examples, 0 failures

[thibaudgg]

@markets thanks for the update. 👍

Yes, some work would be required to fix the build and update it to support the latest Ruby version, but I don't have much time for it now. Please feel free to have a look and submit a PR to improve it.

[thibaudgg]

3.1.0 released.

[miguelpeniche]

Hi there @thibaudgg. There is a minor bug: with the Vimeo user page VideoInfo.valid_url? "https://vimeo.com/user123456789" is returning true.