Upgrade Information (WorkflowGenerator and Benchmarks)

For those who are still using an old version of WorkflowSim please upgrade to the newest version in Github. The difference is that we support a new way of importing workflow file (DAX file, like Montage.xml) generated by WorkflowGenerator (https://confluence.pegasus.isi.edu/display/pegasus/WorkflowGenerator). WorkflowGenerator also provides a few benchmarks for you to evaluate your algorithms. In the new version, we don't use a separate genometime.txt or genomesize.txt. Instead we imbed them into DAX file (like genome.xml), which means you can directly use xml generated by WorkflowGenerator. WorkflowGenerator will imbed time and data information into each task.