Fix parsing of quoted keys (#140)

* Added reproducing test

* Fixed double-quoted paths in object

Author: IgorFedchenko

src/Hocon.Tests/HoconTests.cs

@@ -1,4 +1,4 @@
-//-----------------------------------------------------------------------
+//-----------------------------------------------------------------------
 // <copyright file="HoconTests.cs" company="Hocon Project">
 //     Copyright (C) 2009-2018 Lightbend Inc. <http://www.lightbend.com>
 //     Copyright (C) 2013-2018 .NET Foundation <https://github.com/akkadotnet/hocon>
@@ -230,6 +230,19 @@ public void CanParseObject()
             Assert.Equal("1", Parser.Parse(hocon).GetString("a.b"));
         }
 
+        [Fact]
+        public void CanParseQuotedElements()
+        {
+            var hocon = @"
+A.B = 1
+A {
+ ""X.Y"" = 1
+}
+";
+            var ex = Record.Exception(() => Parser.Parse(hocon).GetObject("A"));
+            Assert.Null(ex);
+        }
+
         [Fact]
         public void CanTrimValue()
         {

src/Hocon/Impl/HoconObject.cs

@@ -171,9 +171,15 @@ public HoconField GetField(HoconPath path)
 
             if (path.Count == 0)
                 throw new ArgumentException("Path is empty.", nameof(path));
-
-            var pathIndex = 0;
+            
             var currentObject = this;
+            
+            // Sometimes path may be a double-quoted string like "a.b.c" with quotes ommited,
+            // so check if there is such key first
+            if (currentObject.TryGetValue(path.ToString(), out var rootField))
+                return rootField;
+            
+            var pathIndex = 0;
             while (true)
             {
                 var key = path[pathIndex];