Fix encoding issue (#11)

Now supports all languages
Tested with korean input

classes.txt

@@ -3,4 +3,4 @@ minivan
 auto
 truck
 minibus
-sedan
+가각

reader.py

@@ -17,6 +17,6 @@ def get_xml_files(self):
 
     @staticmethod
     def get_classes(filename="classes.txt"):
-        with open(os.path.join(os.path.dirname(os.path.realpath('__file__')), filename), "r") as f:
+        with open(os.path.join(os.path.dirname(os.path.realpath('__file__')), filename), "r", encoding="utf8") as f:
             lines = f.readlines()
             return {value: key for (key, value) in enumerate(list(map(lambda x: x.strip(), lines)))}

xml/image-0000016.xml

@@ -7,7 +7,7 @@
 	</size>
 	<segmented>0</segmented>
 	<object>
-		<name>sedan</name>
+		<name>가각</name>
 		<pose>Unspecified</pose>
 		<truncated>0</truncated>
 		<difficult>0</difficult>

xml/subdir/image-0000003.xml

@@ -19,7 +19,7 @@
 		</bndbox>
 	</object>
 	<object>
-		<name>sedan</name>
+		<name>가각</name>
 		<pose>Unspecified</pose>
 		<truncated>0</truncated>
 		<difficult>0</difficult>