Fix XML encoding problem

```
% sbt get-db patch-db run build-dict
[skip]
/Users/jsa/Developer/moedict-mac/moedict_templates
""".."/bin"/build_dict.sh"  "萌典" MoeDictionary.xml MoeDictionary.css MyInfo.plist
- Building 萌典.dictionary.
- Cleaning objects directory.
- Preparing dictionary template.
- Preprocessing dictionary sources.
tr: Illegal byte sequence
Error.
make: *** [all] Error 1
echo "Installing into ~/Library/Dictionaries".
Installing into ~/Library/Dictionaries.
mkdir -p ~/Library/Dictionaries
ditto --noextattr --norsrc ./objects/"萌典".dictionary  ~/Library/Dictionaries/"萌典".dictionary
ditto: can't get real path for source
make: *** [install] Error 1
java.lang.RuntimeException: Build Dictionary failed.
	at scala.sys.package$.error(package.scala:27)
```