Default token_payload doesn't return a random hex value

[nbibler]

The README indicates that if the token_payload is left unset, then it:

Defaults to a randomly generated token in a hash: { token: "RANDOM-TOKEN" }

However, that is not this library's current behavior.

The following is what is actually generated if you fail to set a token_payload:

{
  "token": "#<Method: SecureRandom.hex>"
}

The token payload's default value does not appear to be getting called (the hex method reference is simply being converted to a string) and no random hash is generated:

doorkeeper-jwt/lib/doorkeeper/jwt/config.rb

Lines 112 to 115 in 25223d6

	option(
	:token_payload,
	default: proc { { token: SecureRandom.method(:hex) } }
	)

[ransombriggs]

I can confirm this, I started with an empty config and noticed this as well when testing.

[ransombriggs]

I pushed up a fix for this issue: #56

[nbibler]

Thank you, @ransombriggs!