Plotting of Intan RHD files fails when plots metadata is unspecified

[jpgill86]

The Intan RHD example file added in PR #324 (created by the Intan RHX recording software in demo mode) cannot be plotted properly unless the list of channels to plot is given explicitly (hence this was added to metadata-for-tests.yml).

If plots metadata is omitted, the display looks like this:

The following error appears in the console:

Traceback (most recent call last):
  File "c:\users\jeffr\documents\python-dev\ephyviewer\git-repo\ephyviewer\ephyviewer\traceviewer.py", line 370, in on_request_data
    sigs_chunk, dict_scatter = self.get_data(t, t_start, t_stop, total_gains, total_offsets, visibles, decimation_method)
  File "c:\users\jeffr\documents\python-dev\ephyviewer\git-repo\ephyviewer\ephyviewer\traceviewer.py", line 297, in get_data
    sigs_chunk = self.source.get_chunk(i_start=i_start, i_stop=i_stop)
  File "c:\users\jeffr\documents\python-dev\ephyviewer\git-repo\ephyviewer\ephyviewer\datasource\neosource.py", line 215, in get_chunk
    sigs = self.neorawio.get_analogsignal_chunk(block_index=self.block_index, seg_index=self.seg_index,
  File "c:\users\jeffr\documents\python-dev\neo\git-repo\python-neo\neo\rawio\baserawio.py", line 574, in get_analogsignal_chunk
    raw_chunk = self._get_analogsignal_chunk(
  File "c:\users\jeffr\documents\python-dev\neo\git-repo\python-neo\neo\rawio\intanrawio.py", line 156, in _get_analogsignal_chunk
    sigs_chunk[:, i] = data_chan[block_start:block_stop].flatten()[sl0:sl1]
ValueError: could not broadcast input array from shape (704,) into shape (2814,)