add Coveralls coverage badge to README
add Coveralls coverage badge to README

zacechola/bootlint,angeliaz/bootlint,2947721120/ubiquitous-octo-kumquat,fellipecouto96/bootlint,cnbin/bootlint,evilemon/bootlint,kkirsche/bootlint,twbs/bootlint,cnbin/bootlint,kkirsche/bootlint,kkirsche/bootlint,zacechola/bootlint,2947721120/ubiquitous-octo-kumquat,iamphill/bootlint,evilemon/bootlint,zacechola/bootlint,freezy-sk/bootlint,angeliaz/bootlint,2947721120/ubiquitous-octo-kumquat,iamphill/bootlint,chrismbarr/bootlint,chrismbarr/bootlint,freezy-sk/bootlint,freezy-sk/bootlint,techkrish/bootlint,techkrish/bootlint,fellipecouto96/bootlint,evilemon/bootlint,cnbin/bootlint,fellipecouto96/bootlint,angeliaz/bootlint,iamphill/bootlint,chrismbarr/bootlint,techkrish/bootlint,twbs/bootlint