Adding an option to run git blame -w

[StyMaar]

Hello,

I love this package, the only thing that is currently missing ihmo is the possibility to configure git blame to be runned with the -w option to ignore whitespaces.
I don't really use git blame without this option so for now I've just edited the blame method of gitCommander.js to add the -w option but it will be cool if this features was built-in.

Thanks,

[Alex Corre]

i'll make this configurable in settings, but seems like a fine change to me.

[StyMaar]

great ! Thanks for your reactivity !