Merge pull request #181 from niedbalski/master

Readme modified for table creation/drop on multiple models.
Do not generate empty insert statements, fixes #182
Fixing the table name generator in pwiz
Adding a section to docs for use with other databases.
Too much markdown lately
Adding ``iterator`` as a method on SelectQuery as short-hand for
``.execute().iterator()``
Merge remote-tracking branch 'upstream/master'
peewee.py: Query where method, added kwargs options, first option used is the operator ( used for multiple where conditions ) to specify the kind of operator ( OP_AND, OP_OR)