Adding new has_key_for? method to params

[jwoertink]

Fixes #72
This is another in the #369 series.

This doesn't really do much in Avram itself since most of the implementation comes from Lucky::Params.

[jwoertink]

Since Avram::Params are mainly used to circumvent some testing stuff, the actual specs for this will go in Lucky itself.

[paulcsmith]

I think specs should definitely be here so we know we don't break Avram.

I think we can still test this by making a fake class that implements this Paramable and then tests that it returns the right thing.

See example here:

avram/spec/operations/nested_save_operation_spec.cr

Lines 17 to 58 in 79668a9

	private class NestedParams
	include Avram::Paramable
	@business : Hash(String, String) = {} of String => String
	@email_address : Hash(String, String) = {} of String => String
	@tax_id : Hash(String, String) = {} of String => String
	def initialize(@business, @email_address, @tax_id)
	end
	def nested?(key : String) : Hash(String, String)
	if key == "email_address"
	@email_address
	elsif key == "tax_id"
	@tax_id
	elsif key == "business"
	@business
	else
	raise "What is this key!? #{key}"
	end
	end
	def nested(key : String) : Hash(String, String)
	nested?(key)
	end
	def get?(key)
	raise "Not implemented"
	end
	def get(key)
	raise "Not implemented"
	end
	def nested_file?(key)
	raise "Not implemented"
	end
	def nested_file(key)
	raise "Not implemented"
	end
	end

[jwoertink]

I'm gonna merge this in so I can update the Lucky PR