Merge pull request #29 from oreillymedia/sarah-passthrough

adding tests, and improving passthrough handling in standalone conversion script
adding better handling for partintro divs
Merge pull request #30 from oreillymedia/sarah

adding better handling for partintro divs
making sure htmlbook-autogen templates match htmlbook templates, except for document template
Merge pull request #31 from oreillymedia/sarah

making sure htmlbook-autogen templates match htmlbook templates
fixed placement of quotation mark after alt attribute; fixes #32
Merge pull request #33 from oreillymedia/sarah

fixed placement of quotation mark after alt attribute
few tweaks to convert_passthroughs.rb standalone script