dropped a2ps and out option, clean up

cwdiff: fix --diffopts option (fixes #4)

fixed Makefile

cwdiff: moved issue tracker to github

cwdiff: included a patch from NetBSD

cwdiff: allow 1st argument begin a file with --filter

cwdiff: do not expand escape sequences in diff

cwdiff: fixed deleted leading spaces

cwdiff: replace usage of mktemp with bash built-ins

cwdiff: fixed a bug if argument were dirs