Merge pull request #17 from PatrickDeelen/master

A lot of refactoring
Fix iterator bug
Merge pull request #18 from erwinwinder/master

Fix iterator bug
Moved Plink utils from molgenis to molgenis-genotype-reader
Merge pull request #19 from joerivandervelde/master

Plink utils migration
Merge branch 'master' of https://github.com/molgenis/molgenis-genotype-reader
Restoring some test and small improvements