add dbg exit field, add error warn

Author: PSeitz

snippets/dbg.sublime-snippet

@@ -1,5 +1,5 @@
 <snippet>
-    <content><![CDATA[dbg!($0)]]></content>
+    <content><![CDATA[dbg!($1);$0]]></content>
     <scope>source.rust</scope>
     <tabTrigger>dbg</tabTrigger>
     <description>dbg!(…)</description>

snippets/error.sublime-snippet

@@ -0,0 +1,6 @@
+<snippet>
+    <content><![CDATA[error!("${1:\{${2::?}\}}"${1/([^\{])*(\{.*\})?.*/(?2:, :\);)/}$3${1/([^\{])*(\{.*\})?.*/(?2:\);)/}]]></content>
+    <scope>source.rust</scope>
+    <tabTrigger>error</tabTrigger>
+    <description>error!(…)</description>
+</snippet>

snippets/warn.sublime-snippet

@@ -0,0 +1,6 @@
+<snippet>
+    <content><![CDATA[warn!("${1:\{${2::?}\}}"${1/([^\{])*(\{.*\})?.*/(?2:, :\);)/}$3${1/([^\{])*(\{.*\})?.*/(?2:\);)/}]]></content>
+    <scope>source.rust</scope>
+    <tabTrigger>warn</tabTrigger>
+    <description>warn!(…)</description>
+</snippet>