Add Equal validator

[tuukkamustonen]

Adds a validator for matching equal values, e.g. Equal([]). Saves you from typing All(list, Length(max=0)). Or maybe do Equal({}) when you have extra=True.

[tusharmakkar08]

Merged 🍰
Can you please also update the documentation in branch gh-pages ?

[tuukkamustonen]

@tusharmakkar08 I can, but what do you want me to put there? Equal will be auto-included into the validators page, afaik.

[tusharmakkar08]

@tuukkamustonen : Yes, but you need to remake the documentation after pulling from master. Also create the PR for the same.

[tuukkamustonen]

@tusharmakkar08 Sorry, I'm not familiar with gh-pages.

Should I make a dummy commit and PR? Or merge master to gh-pages and PR? Or rebase on master (that would require force push I guess)?

[alecthomas]

@tuukkamustonen It might be an idea to create a Wiki page describing how to update the documentation, then we can point contributors to it.

[tusharmakkar08]

@tuukkamustonen : Just merge the master into gh-pages and then follow this: https://github.com/alecthomas/voluptuous/tree/gh-pages#contribution-to-documentation. Let me know if you still face any issue.
Yes, we can create a Wiki page for describing how to update the documentation.