Added revdep checking

added reverse dependency check

white space

update comments and added echo for exec status

simplified revdep_check

put revdep inside 'if' block with cmd arg

only send package name

save output and print it

updated to checkoutput and for errors.  exit with status = 1 if errors

try to print errors for revdep_check

typo

print check error file in console

output formatting

print checkOutput in a data.frame

typo

removed stringr dependency

added sample_revdeps.travis.yml file

added note about revdep setup

spacing

wording
Merge pull request #122 from schloerke/rev_deps_squash

Added revdep checking