update readme with dplyr video link
update readme with dplyr video link

meganclarke/STT2810ClassRepo,meganclarke/STT2810ClassRepo,rachaelgossett/STT2810ClassRepo,aimeesinclair/STT2810ClassRepo,STAT-ATA-ASU/STT2810ClassRepo,STAT-ATA-ASU/STT2810ClassRepo,mningle/STT2810ClassRepo,STAT-ATA-ASU/STT2810ClassRepo,mningle/STT2810ClassRepo,aimeesinclair/STT2810ClassRepo,kenleyplott/STT2810ClassRepo,STT2810-ASU/STT2810ClassRepo,alanarnholt/STT2810ClassRepo,kenleyplott/STT2810ClassRepo,alanarnholt/STT2810ClassRepo,STT2810-ASU/STT2810ClassRepoSP15,STT2810-ASU/STT2810ClassRepoSP15,STT2810-ASU/STT2810ClassRepo,rachaelgossett/STT2810ClassRepo