Chisel implementations

Hey,

There is only one version of VTA in Chisel. As the name suggest, tsim_example is an example of TSIM (cycle accurate simulation) for a really simple accelerator using some components of VTA, i.e. DPI.

This Chisel version is currently passing all microbenchmarks/tests except end-to-end things like ResNet. There is still some work-to-do on this end.