Tractor v1.4.0

1. Added support for compressed (gz) hapcount/dosage and phenotype files.
2. Improved file reading efficiency by implementing fread in chunks, mitigating memory errors.
   • Use --chunksize to define number of lines from the file read. Default: 10000
3. Implemented parallel processing for regression, resulting in significant speed improvements with multi-core systems.
   • Use --nthreads to identify the number of threads for parallel processing.
4. Enhanced flexibility in organizing phenotype files:
   • Users can specify sample ID column (--sampleidcol), phenotype ID column (--phenocol), and covariate column list (--covarcollist)
5. Updated output summary statistics to include SE and t-val, with column names adjusted to adhere to GWAS standards.