fixing linter issues

fixing linter issues

added variable to allow configuration of mousetrap message duration (s…

…pf13#809)

new variable MousetrapDisplayDuration allows to modify the default
display duration of 5s, or to completely disable the timeout and wait
for the user to press the return key.

Fixed code sample for bash completion (spf13#687)

Update the Travis and CircleCI Go versions (spf13#651)

Create new buffer if not present yet (spf13#549)

Fixes a nil dereference when TraverseChildren is used
with multiple subcommands.