Yaml format chokes on TSV when detecting

[bracki]

See here:

======================================================================
ERROR: Test YAML format detection.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jbrauer/projects/tablib/test_tablib.py", line 486, in test_yaml_format_detect
    self.assertFalse(tablib.formats.yaml.detect(_tsv))
  File "/home/jbrauer/projects/tablib/tablib/formats/_yaml.py", line 58, in detect
    _yaml = yaml.safe_load(stream)
  File "/usr/lib/python2.6/dist-packages/yaml/__init__.py", line 75, in safe_load
    return load(stream, SafeLoader)
  File "/usr/lib/python2.6/dist-packages/yaml/__init__.py", line 58, in load
    return loader.get_single_data()
  File "/usr/lib/python2.6/dist-packages/yaml/constructor.py", line 42, in get_single_data
    node = self.get_single_node()
  File "/usr/lib/python2.6/dist-packages/yaml/composer.py", line 35, in get_single_node
    if not self.check_event(StreamEndEvent):
  File "/usr/lib/python2.6/dist-packages/yaml/parser.py", line 93, in check_event
    self.current_event = self.state()
  File "/usr/lib/python2.6/dist-packages/yaml/parser.py", line 138, in parse_implicit_document_start
    StreamEndToken):
  File "/usr/lib/python2.6/dist-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/usr/lib/python2.6/dist-packages/yaml/scanner.py", line 257, in fetch_more_tokens
    % ch.encode('utf-8'), self.get_mark())
ScannerError: while scanning for the next token
found character '\t' that cannot start any token
  in "<string>", line 1, column 4:
    foo bar
       ^

[kennethreitz]

I merged in your change, thanks!