rust: add snippets for crate, pub fns, and constructor (#262)

snippets/rust-mode/crate

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: extern crate
+# key: ec
+# --
+extern crate ${0:name};

snippets/rust-mode/new

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: fn main() { ... }
+# key: new
+# --
+pub fn new($1) -> ${2:Name} {
+   $2 { ${3} }
+}

snippets/rust-mode/pfn

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: pub fn name() { ... }
+# key: pfn
+# --
+pub fn ${1:name}($2) {
+    $0
+}

snippets/rust-mode/pfnr

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: pub fn name() -> Type { ... }
+# key: pfnr
+# --
+pub fn ${1:name}($2) -> ${3:Type} {
+     $0
+}

snippets/rust-mode/pfns

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: pub fn name(&self) -> Type;
+# key: pfns
+# --
+pub fn ${1:name}(${2:&self}) -> ${3:Type};

snippets/rust-mode/pfnw

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: pub fn name<T>(x: T) where T: Clone { ... }
+# key: pfnw
+# --
+pub fn ${1:name}<${2:T}>(${3:x: T}) where ${4:T: Clone} {
+     $0
+}