add support convert from snake case

Source/Configuration.swift

@@ -25,6 +25,8 @@ public struct DeserializeOptions: OptionSet {
     public let rawValue: Int
 
     public static let caseInsensitive = DeserializeOptions(rawValue: 1 << 0)
+
+    public static let convertFromSnakeCase = DeserializeOptions(rawValue: 1 << 1)
 
     public static let defaultOptions: DeserializeOptions = []
 

Source/ExtendCustomModelType.swift

@@ -30,6 +30,16 @@ fileprivate func convertKeyIfNeeded(dict: [String: Any]) -> [String: Any] {
             newDict[key.lowercased()] = value
         })
         return newDict
+    } else if HandyJSONConfiguration.deserializeOptions.contains(.convertFromSnakeCase) {
+           var newDict = [String: Any]()
+           dict.forEach({ (kvPair) in
+               let (key, value) = kvPair
+               let result = key.split(separator: "_").reduce("") {(acc, name) in
+                   "\(acc)\(acc.count > 0 ? String(name.capitalized) : String(name))"
+               }
+               newDict[result] = value
+           })
+           return newDict
     }
     return dict
 }

Tests/HandyJSONTests/BasicTypesInStructTestsFromJSON.swift

@@ -112,6 +112,22 @@ class BasicTypesInStructTestsFromJSON: XCTestCase {
         XCTAssertEqual(mappedObject?.anyObjectOptional as? Int, value2)
         XCTAssertEqual(mappedObject?.anyObjectImplicitlyUnwrapped as? Double, value3)
     }
+
+    func testMappingAnyObjectFromJSONByConvertFromSnakeCase() {
+        HandyJSONConfiguration.deserializeOptions = .convertFromSnakeCase
+        defer {
+            HandyJSONConfiguration.deserializeOptions = .defaultOptions
+        }
+        let value1 = "STRING"
+        let value2: Int = 1234
+        let value3: Double = 11.11
+        let JSONString = "{\"any_object\" : \"\(value1)\", \"any_object_optional\" : \(value2), \"any_object_implicitly_unwrapped\" : \(value3)}"
+        let mappedObject = BasicTypesInStruct.deserialize(from: JSONString)
+        XCTAssertNotNil(mappedObject)
+        XCTAssertEqual(mappedObject?.anyObject as? String, value1)
+        XCTAssertEqual(mappedObject?.anyObjectOptional as? Int, value2)
+        XCTAssertEqual(mappedObject?.anyObjectImplicitlyUnwrapped as? Double, value3)
+    }
 
     func testMappingStringFromNSStringJSON(){
         let value: String = "STRINGNGNGG"