Drop unnecessary tags (e.g. created_by)

This patch adds an option to specify a list of tags to drop but will
always drop created_by, odbl and odbl:note

closes #11
Fix bug where we were generating invalid XML
Add the framework of some better docs
Create a new column in the import_addresses table with a buffered geometry
Add code to merge addresses onto existing buildings (See issue #4)

This currently only handles buildings as ways.

It will avoid merging onto a building if there are multiple addresses
within or very near it in either the import source or in OSM
Fix node change returns
Make the view as temporary explicitly instead of implicitly
Finalize the SQL for matching buildings. This finishes the code
for issue #3 but not the docs
Change the logic for building matching to use --building everywhere except the inital match and to prefilter with a manually computed degree-based bounding box expansion
Add documentation for --building and other options

This closes #3