Correct string syntax & fix issue#42

Author: zxh0

syntaxes/proto3.JSON-tmLanguage

@@ -244,8 +244,7 @@
       "name": "storage.type.proto"
     },
     "string": {
-      "begin": "\"",
-      "end": "\"",
+      "match": "('([^']|\\')*')|(\"([^\"]|\\\")*\")",
       "name": "string.quoted.double.proto"
     },
     "number": {

syntaxes/proto3.tmLanguage

@@ -637,12 +637,10 @@
       </dict>
       <key>string</key>
       <dict>
-        <key>begin</key>
-        <string>"</string>
-        <key>end</key>
-        <string>"</string>
         <key>name</key>
         <string>string.quoted.double.proto</string>
+        <key>match</key>
+        <string>('([^']|\')*')|("([^"]|\")*")</string>
       </dict>
       <key>number</key>
       <dict>