Fixing two issues:     - the regular expression used to match substitution values was not account for spaces or ! characters     - the optenv default value was not being handled properly
Fixing two issues:
    - the regular expression used to match substitution values was not account for spaces or ! characters
    - the optenv default value was not being handled properly

bponsler/roslaunch_to_dot,bponsler/roslaunch_to_dot