Add IMEI to PhoneNumber

[wemcdonald]

Add valid IMEI (cell phone UUID) generator to PhoneNumber using proper reserved IMEIs

[rstacruz]

Error: test_imei_with_sn(TestPhoneNumer): NameError: uninitialized constant TestPhoneNumer::Faker

/home/travis/build/EmmanuelOga/ffaker/test/test_phone_number.rb:20:in `test_imei_with_sn'
     17: 
     18:   def test_imei_with_sn
     19:     sn = rand(1_000_000)
  => 20:     assert_match /^\d{8}#{sprintf('%06d', sn)}\d{1}$/, Faker::PhoneNumber.imei(sn)

Thanks for the contribution! Might have missed an F in there.

[wemcdonald]

Ah, sorry! This was a cherry-pick from an old branch when it was Faker; fixed.