Add a simple single_snp example of notebook. Also switch notebook's single_snps calls from log_delta to h2
Add a simple single_snp example of notebook. Also switch notebook's single_snps calls from log_delta to h2

zhonghualiu/FaST-LMM,zhonghualiu/FaST-LMM,MicrosoftGenomics/FaST-LMM,MicrosoftGenomics/FaST-LMM,zhonghualiu/FaST-LMM,MicrosoftGenomics/FaST-LMM