remove comments - not relevant to diffing
provide way to specify number of lines of context
make sure _compare database gets cleaned up if errors occur
selectively ignore nothing, comments, 'ADD CONTSTRAINT' (which has generated random name)
Fix syncdb, make it work on empty databases again

The --skip-migrations flag will make it skip the nashvegas migrations,
which will fail on new, empty databases. This will also make 'comparedb'
work again if there are migrations in general.
whitespace fixes
Merge pull request #52 from iivvoo/master

comparedb improvements (ignoring, more context, error handling)