0.2-1

  *   Computing the time-line avoids duplicate variables.

  *   Time-line plot has better default for the margins so that variable names appear
      more completely.

0.2-0

  *  Added parameters inputs and free to getVariables() and makeVariableGraph() to allow 
     free/global variables in the graph.

  *  Introduced the notion of update variables for a task/expression as an extension
     of inputs and outputs. These are variables whose contents are assigned values
     via expressions such as names(x) = ..., x$foo = ... and so on.

  *  Documented runUpToSection() and changed the default value for all to TRUE.
