Snippet Injection for Function Autocompletion

[yoo]

Functions are completet as snippets with its parameters as tabstops.
Exampels:
func foo(bar string) -> foo(${1:bar string})
Fuctions as parameters are allowed too:
func foo(f func(bar int), baz int) ->
foo(${1:f func(${2:bar int})}, ${3:baz int})

[yoo]

The interface{} type is not selected properly, the '}' is not selected. I think because of atom/snippets#60

[joefitzgerald]

Thank you for your contribution! This inspired me during the rewrite of autocomplete-plus, such that the ability to insert snippets will be handled by autocomplete-plus directly. Thanks so much for thinking out of the box on this.

[yoo]

I rebased my changes and cleaned up the commit history.
The function completion now uses the build in snippet magic of autocomplete-plus