Unicode decode issues CSV output

[stephenfin]

As discussed at #46 (comment)

...I'm now seeing a Unicode issue in another case.

Here is a dump from the DPDK patchwork which works:

$ git-pw patch list "bulk" --column ID --column Submitter
+-------+------------------------------------------+
|    ID | Submitter                                |
|-------+------------------------------------------|
| 59113 | Morten Brørup (mb@smartsharesystems.com) |
+-------+------------------------------------------+

However, with the CSV output it throws an exception

$ git-pw patch list "bulk" --column ID --column Submitter -f csv
Traceback (most recent call last):
  File "/usr/bin/git-pw", line 10, in <module>
    sys.exit(cli())
  File "/usr/lib/python2.7/site-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python2.7/site-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python2.7/site-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python2.7/site-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python2.7/site-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/git_pw/api.py", line 303, in new_func
    return ctx.invoke(f, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/git_pw/patch.py", line 265, in list_cmd
    utils.echo_via_pager(output, headers, fmt=fmt)
  File "/usr/lib/python2.7/site-packages/git_pw/utils.py", line 155, in echo_via_pager
    _echo_via_pager('less', output)
  File "/usr/lib/python2.7/site-packages/git_pw/utils.py", line 113, in _echo_via_pager
    c.stdin.write(line.encode(encoding, 'replace'))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 0: ordinal not in range(128)
"ID","Submitter"
"59113","Morten Br

[john-mcnamara-intel]

Just to confirm that this now works as expected. Thanks.