Can't read UTF-16 XML files

[shpiyu]

Describe the bug
I tried reading an XML file that is encoded in UTF-16 but ingen could not read it. It creashed with UnicodeDecodeError while trying to read using my mahcine's default encoding (utf-8).

To Reproduce
Steps to reproduce the behavior:

1. Create a XML file with UTF-16 encoding
2. Try to read it via InGen by adding it as a data source
3. See error:

Expected behavior
InGen should read UTF-16 files without crashing

Environment (please complete the following information):

• Operating System: Mac

Additional context
We should add an option in the FileSource for users to declare the file encoding.

[ChillarAnand]

This is fixed in #46