made fixreader/writer virtual execute call from non-virtual operator()
Merge pull request #28 from syegres/fixfor_fx-147

made fixreader/writer virtual execute call from non-virtual operator()
FX-139 Make includes relative to project root
Merge branch 'master' of github.com:dakka/fix8
Merge branch 'master' of https://github.com/syegres/fix8 into fixfor_fx-116

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