Allow to pass Diplomat::Configuration object when using diplomat

[kamaradclimber]

(Not a very good issue description, feel free to rename it)

Let's consider the following scenario:

• a first piece of code defines a consul token using:

Diplomat.configure do |c|
  c.token = A
end

• a second piece of code (different library or maybe chef cookbook) defines another consul token (B).

• the first piece of code later calls diplomat assuming the token is A.

In this case, you might encounter an unauthorized error.

The issue is that Diplomat::Configuration is static. In an ideal world we should be able to do:

my_conf = Diplomat::Configuration.new.tap do |c|
  c.token = 'aaaaa'
end
Diplomat::Service.new(my_conf).get_all

What do you think?