added --coal-counts and --zero-branches options to arg-summarize
first cut at sampling phasings
Merge branch 'master' of virgil:~/argweaver.git_bare

Conflicts:
	src/arg-sample.cpp
	src/model.h
speed up compress_mask function
Merge branch 'master' of virgil:~/argweaver.git_bare

Conflicts:
	src/arg-summarize.cpp