Update esprima version to 2.7.1

Author: Constellation

package.json

@@ -33,7 +33,7 @@
     "dependencies": {
         "estraverse": "^1.9.1",
         "esutils": "^2.0.2",
-        "esprima": "^1.2.2",
+        "esprima": "^2.7.1",
         "optionator": "^0.5.0"
     },
     "optionalDependencies": {