sc_auto_complete method argument completion

Hey,

I hacked together a method argument auto-completion implementation as I was getting really jealous of that feature in the new IDE.You can also find it as an individual plugin (and detailed instructions) at [dathinaios/sc_auto_complete] (https://github.com/dathinaios/sc_auto_complete). I will be editing the scvim README file with additions.

Feel free to give feedback or make suggestions!

best,

Dionysis