typo
Merge pull request #62 from scraperdragon/typo

typo
Test for unknown extension, fix typo in error formatting
Merge pull request #63 from scraperwiki/unknownextension

Test for unknown extension, fix typo in error formatting
upstream merge
no duplicate horror
Merge pull request #60 from scraperdragon/htmltableset

HTMLTableSet
Add missing lxml dependency to setup.py
Improve readme.md
Update readme
Add contributing file
Move html tests to the end of test_read
Suggest to use PEP8 in contributing file
Extend contributing guidelines
merge with okfn