send SUSEConnect/package version in USER-AGENT header
Specify which attributes should be serialized
improve error message
add extensions list to product model
Improve config class to reuse existing classes and improve API

For holding values it is better to use Struct that gives required
flexibility. Also have smaller and cleaner API.
change format of zypper product identifier to <internal name>/<version>/<architecture>
refactor integration steps
add integration tests for language and extension activation
fix rubocop warnings
mute rubocop
Merge pull request #92 from SUSE/review_140602_send_suseconnect_package_version_in_user_agent_headersend_suseconnect_package_version_in_user_agent_header

[Review] Request from 'vlewin' @ 'SUSE/connect/review_140602_send_suseconnect_package_version_in_user_agent_headersend_suseconnect_package_version_in_user_agent_header'
config: fix convert to string
fix where rubocop complain
update rspec syntax
fix rspec syntax
require date
rspec: use be (true)
add useragent
fix return value on unavailable credentials file
fix rspec syntax