fix syntax highlighting for ! and != (#9)

Author: rpadaki

syntaxes/solidity.tmLanguage.json

@@ -194,7 +194,7 @@
             ]
         },
         "operator-logic": {
-            "match": "(==|<(?!<)|<=|>(?!>)|>=|\\&\\&|\\|\\||\\:(?!=)|\\?)",
+            "match": "(==|\\!=|<(?!<)|<=|>(?!>)|>=|\\&\\&|\\|\\||\\:(?!=)|\\?|\\!)",
             "name": "keyword.operator.logic"
         },
         "operator-mapping": {