Docs around mocking based on parts of the input

[mrjoelkemp]

I had the very case that I included as a bullet point in the docs. I didn't see an obvious way to do it with Mock because the examples were assuming you wanted to mock based on the exact input value. I wanted to mock based on parts of the input value. I figured out how to do it with Mock and thought it would be helpful for others to have explicit docs around this.

Happy to change any of the language. Thanks for the great library.

[coveralls]

Coverage remained the same at 100.0% when pulling 5809dba on mrjoelkemp:patch-1 into 0e07a6e on jjh42:master.

[Olshansk]

Instead of creating a whole different section for this, maybe simply updat ethe documentation above to be

     get: fn
        (%{}, "http://example.com") ->
        (%{}, "http://example.org") ->
        (%{}, url) -> foo(url)

def foo(url) do
   cond do
   end
end

Let me know what you think!

[mrjoelkemp]

Done! Thanks for the suggestion.