QQ plots w. confidence bands

[ttfiliz]

Fixes #37

Changes proposed in this pull request:

• GWASTools is now used for qq plots instead of qqman
• Added GWASTools package to r.sif

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[espenhgn]

Thanks @ttfiliz,
I don't know if your PR is ready for review yet. In either case, can you also update the CHANGELOG file with these changes?

[ttfiliz]

Thank you @espenhgn,
I have updated the changelog file.