[data file parsing] improve speed and efficiency when parsing IndSeq SNP data file

[gdurif]

• [ ] enable multi-threading on Windows
• [ ] improve result row binding in function check_snp_indseq
• [ ] do some profiling and find some possible improvements

[gdurif]

See #22 and #65 for additional information regarding multi-threading on Windows

[gdurif]

Linked with #98