support running rust

a bit hacky, using a wrapper script, because i can't seem to find a flag
for rustc that builds and runs a rust file.

go/linguaevalia/bin/run-rust

#!/bin/sh
rustc $1 && ./`basename $1 .rs`

go/linguaevalia/linguaevalia.go

var Ruby = LanguageGeneral{"Ruby", "rb", "ruby", []string{}}
var JavaScript = LanguageGeneral{"JavaScript", "js", "node", []string{}}
var Haskell = LanguageGeneral{"Haskell", "hs", "runhaskell", []string{}}
var Rust = LanguageGeneral{"Rust", "rs", "./bin/run-rust", []string{}}
var languageMappings = map[string]Language{
	"go":         Go,
	"ruby":       Ruby,
	"javascript": JavaScript,
	"haskell":    Haskell,
	"rust":       Rust,
}
func writeCode(code string, extension string) (*os.File, error) {