Log Message:
Update to 0.3.
v0.3
      * Changed default spring length to 0 and default spring constant to 1
      * Made dot file import more robust:
        * Reports if it doesn't seem to be a dot file rather than blindly
          trying to open it
        * Accounts for more dot syntax
        * doesn't segfault on any of the graphviz examples
      * Made graphopt file opening more robust:
        * Reports if it doesn't seem to be a graphopt file rather than
          blindly trying to open it

v0.2
      * Changed references to vector to std::vector, making compliant with
        latest c++ standards (a la gcc 3)