Updated PUMS links and miscellaneous improvements

[janowicz]

Thanks @jiffyclub for the help with these changes.

This pull request includes the following:

• The previous PUMS links were updated with working ones
• PUMS records associated with both 2000 and 2010 PUMA geography can be used
• Remove loop in frequency table generation for better performance
• Alternative recipe (recipe2) with control variable modifications and addition of new controls
• Appending location identifiers (e.g. block group id) to the synthesized households
• Scripts to reslice PUMS files and relate tracts to the 2000 PUMA geography (in addition to 2010)
• Some minor fixes

[jiffyclub]

Failures are all PEP8 related, which I'll clean up in a subsequent PR.

[fscottfoti]

Pretty sweet.