Adds domain option for Internet email and domain_name methods

[tiagofsilva]

Issue #1624

Example:

Internet.email(name: 'jane doe', domain: 'customdomain')
#=> jane.doe@customdomain.co

Description:

This PR's main goal is to add another option to Internet.email method (fixes #1624), which is the domain param. Also makes possible to generate a domain_name with a custom domain and random subdomain.

[olleolleolle]

@tiagofsilva One cool thing is that if you include the words Fixes #1624 in the Description box, GitHub will auto-close that Issue on merge of this PR.

The PR looks grand and solves my problem perfectly!

[vbrazo]

Looks good, however we're missing documentation in this PR. Please add them!

[olleolleolle]

doc/default/internet.md:

About the email section: add domain

# Keyword arguments: name, separators, domain

Add an example:

Faker::Internet.email(domain: 'example.com') #=> alice@example.com"

And in the domain section, add notes about it, too:

# Keyword arguments: subdomain, domain
Faker::Internet.domain_name #=> "effertz.info"
Faker::Internet.domain_name(domain: "example.com") #=> "example.com"
Faker::Internet.domain_name(subdomain: true, domain: "example.com") #=> "horse.example.com"

[tiagofsilva]

Thanks @olleolleolle and @vbrazo ! Here are the documentation's changes.

[vbrazo]

Sweet. Thanks 💥

[ngouy]

just realized that "subdomain" isn't a valid param for "email"