Using https for github access to rabit library #168

Job	Run time
build+test (linux, gfortran, openmp=yes, release=yes)	10m 3s
build+test (linux, gfortran, openmp=yes, release=no)	9m 54s
build+test (linux, gfortran, openmp=no, release=yes)	13m 51s
build+test (linux, gfortran, openmp=no, release=no)	13m 1s
build+test (linux, ifort, openmp=yes, release=yes)	19m 36s
build+test (linux, ifort, openmp=yes, release=no)	14m 31s
build+test (linux, ifort, openmp=no, release=yes)	22m 32s
build+test (linux, ifort, openmp=no, release=no)	20m 30s
build+test (macos, gfortran, openmp=yes, release=yes)	15m 32s
build+test (macos, gfortran, openmp=yes, release=no)	15m 14s
build+test (macos, gfortran, openmp=no, release=yes)	21m 1s
build+test (macos, gfortran, openmp=no, release=no)	28m 54s
build+test (macos, ifort, openmp=yes, release=yes)	30m 55s
build+test (macos, ifort, openmp=yes, release=no)	22m 23s
build+test (macos, ifort, openmp=no, release=yes)	45m 48s
build+test (macos, ifort, openmp=no, release=no)	31m 50s
benchmark (gfortran)	5m 22s
benchmark (ifort)	4m 57s
release	0s
	5h 45m 54s

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