Added osmparser.py  imposm.parser is now used if installed, but not
required.  Paves the way for install on Windows.
spiderosm_berkeley and spiderosm_portland working with overpass (no
imposm.parser)
TODO: currently fixed filepath being used for overpass download.
Removed fixed path for overpass downloads: using temp file now.
Updated README.txt  Added default location for city and osm pnwk files
to match.py (so that no OSM url/file locations required at all:  OSM
just automagically imported via overpass API. :)
Fixed typo in setup.py
Added virtualenvs to .gitignore