improved common methods of data objects
added country code support to specify returned currency
added travis config
added jdk version
changed jdk to oracle 8
Merge branch 'development' of https://github.com/go-ive/steam-api.git
into development

Conflicts:
	.travis.yml
changed to oracle jdk8
assignment of categories and resultMaps containing more than one game is
now parallel (java 8 feature)
adapted version
not ready
quick update
multiple retrievals possible
Merge branch 'feature_3' into development
added method from pull request by KingFaris10. was the easiest way to
merge the changes
Merge branch 'development' into release
updated version
Merge branch 'release'

Conflicts:
	README.md