Create a new STDIN format

[timtadh]

create a new standard input format for ./stat.py. Currently the format is very limiting and only allows syntax trees to be passed to the program. Now that gramstat can take other things like coverage information this information needs to be expressible on stdin.

proposal: use a json format

eg.

[
  a list of {
    'filename':str, 
    'ast':str, 
    'coverage':[ 
      a list of {
        'filename':str, 
        'total lines':int, 
        'excuted lines':[list of int]
      }
    ]
  }
]