issue #1671 Add User generator which accepts arguments

[lilisako]

Issue#

#1671

Description:

As stated in #1671, add user agent method to Faker::Internet, which returns a random hash of user information.
Also you can specify which Faker::Internet methods to include to the generated hash.

Faker::Internet.user 
#=> 
{:username=>"kiyoko", :email=>"rudy_wilkinson@stroman.io"}

Faker::Internet.user(:username, :safe_email, :password, :uuid) 
#=> 
{:username=>"dennis", 
:safe_email=>"clemente.jakubowski@example.org", 
:password=>"D6uPdDlO4cBb", 
:uuid=>"bf853523-241b-484e-8bab-c9649cc622ed"}