fix bug for default value as proc when there is given options values

[ShPakvel]

When you have option default as a proc and also any kind of option values (as a proc or normal) the gem is crashed. This small change solves it.

[dblock]

Can you please update CHANGELOG? For future googling purposes, also, what's 'crashes'? What's the specific error?

[ShPakvel]

Using grape you can meet error like 'block (2 levels) in <class:API>': wrong number of arguments (1 for 0) (ArgumentError) with code like:

params do
  optional :type, values: ['valid-type1', 'valid-type2'], default: -> { ['valid-type1', 'valid-type2'].sample }
end
get '/default_lambda' do
  { type: params[:type] }
end

params do
  optional :type, values: -> { ValuesModel.values }, default: -> { ValuesModel.values.sample }
end
get '/default_and_values_lambda' do
  { type: params[:type] }
end

And this PR fixes this bug. The problem was about default option value is proc when used with values. There was not call in place which checks inclusion if default in values.

[ShPakvel]

@dblock I've added info to changelog and put some description of the problem here.
Let me know if you need something else.

[dblock]

Merged via 00e745e, changed the language in the CHANGELOG a bit (and put back the your contribution here note).