Update README.md
Merge pull request #35 from fabienbaron/patch-1

Update README.md
Update README.md
Merge pull request #36 from fabienbaron/patch-3

Update README.md
Refactoring, adding more explicit error codes, changing benchmark command line arguments.
Added option to change number of iterations over which timing is conducted. Also added stubs for chaning the number of UV points in the model.
Modified DFT kernel to accept arbitrary-size images. This closes #16.