Create nested-equals matcher

[gilvan-reis]

Create nested-equals function to match nested maps with equals and providing a documentation closer to the code about the nested behavior for matchers.

Closes https://github.com/nubank/matcher-combinators/issues/217

[philomates]

other possible names for deep-equals:

• equals-as-default: has the benefit where default keys the reader to the fact that there is a default that isn't always equals.
• always-equals
• strict

As a note, the midje implementation had a similar thing, match-equals, but the name isn't so great because it conflates the match construct with the combinators.

[gilvan-reis]

I think we should have equals in the function name, so I decided to follow with strictly-equals WDYT?

[gilvan-reis]

@philomates I have replaced the match-with example in the README. Feel free to inform me if you want to stay with both instead

[gilvan-reis]

I have also added the versions changes to be validated