Wipe the output.html file from previous run by writing a blank one sooner.

As soon as the input file has been read in, we write an output file 
which has 0 species and 0 reactions. The species pictures etc. from the 
previous run have been wiped by this point already, but it can be confusing
to have the previous output file still there when you're running a new job.

Author: rwest

rmg.py

@@ -251,6 +251,10 @@ def execute(args):
     # Read input file
     reactionModel, coreSpecies, reactionSystems, database, seedMechanisms = readInputFile(inputFile)
 
+    # Delete previous HTML file
+    from rmgpy.rmg.output import saveOutputHTML
+    saveOutputHTML(os.path.join(settings.outputDirectory, 'output.html'), reactionModel)
+    
     # Initialize reaction model
     if args.restart:
         reactionModel = loadRestartFile(os.path.join(settings.outputDirectory,'restart.pkl.gz'))
@@ -335,7 +339,6 @@ def execute(args):
 
         # Save the current state of the model core to a pretty HTML file
         logging.info('Saving latest model core to HTML file...')
-        from rmgpy.rmg.output import saveOutputHTML
         saveOutputHTML(os.path.join(settings.outputDirectory, 'output.html'), reactionModel)
 
         # Save a Chemkin file containing the current model core