examples: add modelines

Signed-off-by: Greg Farnum <greg@inktank.com>
examples: use EXIT_SUCCESS, EXIT_FAILURE instead of 0, -1

Signed-off-by: Greg Farnum <greg@inktank.com>
examples: load conf file specified with --conf as well -as -c

Signed-off-by: Greg Farnum <greg@inktank.com>
examples: add a clarifying comment on error checking

Signed-off-by: Greg Farnum <greg@inktank.com>