Open remote tables, be they CSV, XLSX, HTML, XML, ...

Heavily inspired by Seamus Abshere's remote_table gem: a lot of the APIs and even some of the tests are cribbed from there. Thanks, Seamus.

WARNING: This is very rough right now -- more a proof of concept than a working project. But I'd like to see it grow, so please feel free to submit pull requests!

Full docs will come before I consider this done, but they don't exist yet. For a taste, though:

>>> t = remotetable.open('https://raw.github.com/gist/1111189/unruly_passengers.txt', parser='csv')
>>> for row in t:
...     print row['Year'], row['Total']
...
1995 146
1996 184
1997 235
1998 200
1999 226
2000 251
2001 299
2002 273
2003 281
2004 304
2005 203
2006 136
2007 150
2008 123
2009 135
2010 121

>>> t = remotetable.open(
...     url = 'http://police.lawrenceks.org/sites/default/files/files/stats/2011UCR.htm',
...     row_xpath = '//table//table/tr',
...     column_xpath = 'td|th',
...     select = lambda row: row['UCR Classification'] != ''
... )
>>> sum(int(row['Total']) for row in t)
5167