encoding not passed to stream

[pabloh007]

on line 90 of book.py
file_stream = _convert_content_to_stream(file_content, self._file_type)

does not pass the encoding to use so when decode is used later it throws an decoding exception

it should maybe use the **keywords and pass it to the function like so
file_stream = _convert_content_to_stream(file_content, self._file_type, **keywords)

to maybe something like the below. currently the file_content.decode is set to static 'utf-8'

def _convert_content_to_stream(file_content, file_type, **keywords):
    io = manager.get_io(file_type)
    encoding = keywords.get('encoding', 'utf-8')
    if PY2:
        io.write(file_content)
    else:
        if (isinstance(io, StringIO) and isinstance(file_content, bytes)):
            content = file_content.decode(encoding)

[chfw]

Please verify it using pyexcel v0.3.4