add options '--deps-up-to', '--deps-only'; '--exclude', add support for special keywords 'ALL', 'RPP'; implement reverse dependency walk
add check that ROS_PACKAGE_PATH is defined when using RPP
fix issues pointed out in pull request
rename distro option
fix --deps-up-to to include packages requested (when not using --deps-only)
Merge pull request #4 from ros-infrastructure/new_options

add options '--deps-up-to', '--deps-only'; '--exclude', add support for special keywords 'ALL', 'RPP'; implement reverse dependency walk