v1.4.6

MendelIHT v1.4.6

This is the last update before resubmitting our manuscript. The main changes are:

1. fix bug: init_beta not initializing intercept correctly
2. Updated documentation, adding more docstrings and discussion on memory requirement
3. Add lower bound to SnpArrays, which ensures that multithreading with SnpLinAlg is always using Base.Threads
4. Add scripts and output files for new analysis in our paper

Diff since v1.4.5