use "registration code" term everywhere

to be consistent with SCC terminology
Merge pull request #54 from yast/registration_CODE_term

use "registration code" term everywhere
"reg. key" -> "reg. code" also in non-ruby files
Merge pull request #55 from yast/registration_CODE_term

"reg. key" -> "reg. code" also in non-ruby files
use suse-connect gem instead of scc_api
added "suse-connect" gem to Gemfile

to use at Travis builds
pass release_type product attribute (bnc#873194)
share creating the default suse-connect options
cleanup - add_product_services() is used just once
added test/registration_spec.rb
pass distro_target to suse-connect
pass email
exception handling
removed FATE#316796 placeholder
fixes to register the system and the base product
load credentials from system if the system was already registered
updated test
display more details in the exception handler