Added get_group_stats.R and Rd: this function is necessary for haid_plot to work. Fixed small error (extra }) in norm_sim's documentation. updated haid_plot so that p_alpha acutally addusts underlying growth goals alpha values; also changed vjust on growth goals to 0 (so they float about pipe marks).
Merge pull request #4 from chrishaid/master

Updates to haid_plot