Support smerge

[dakra]

I like smerge better than ediff as it's easier and most of the time enough. Magit has smerge as default as well.

[UndeadKernel]

I'm not familiar with smerge but it might be a simple feature to implement. I'll try to experiment with it to see how it works. Ediff is a monsert, but once you learn to use it (and understand it's delicate feelings) it's powerful.