fix params.inspect for document format. use Hash and Proc soucify.

[joker1007]

In case document format,
Hash inspection is easier to see name & value combination.

and, In case I give Proc object to parameters,
sourcify Proc object for readability

[joker1007]

About document format

Sorry. I was lazy to think about document format.
prefererd format is like following:

a: 1, b: 2, c: 3

The code is following:

pretty_params = [arg_names, params].transpose
  .map {|t| "#{t[0].to_s}: #{param_inspect(t[1])}"}.join(", ")
describe(pretty_params, *args) do

# ...

def param_inspect(obj)
  obj.class == Proc ? obj.to_raw_source : obj.inspect
end

I want to use custom format in the future.

About Proc inspection.

I also prefer later code.
I agree with to_raw_source.