sql2csv: adds ability to pass arguments to create_engine

[sgpeter1]

Some of us with peculiar database setups need the ability to pass arguments to the underlying sqlalchemy create_engine function.

I chose to use space-separated key-value pairs, but many alternatives are possible. The syntax looks like this:

--engine-kwargs key1 value1 --engine-kwargs key2 value2

A full example looks like this:

sql2csv --db "oracle+oracledb://user:pass@hostname:port/dbname" --engine-kwargs thick_mode True --query "select trans_id, total_cost from transactions"

[coveralls]

coverage: 90.281% (-0.1%) from 90.393%
when pulling 93d35b9 on sgpeter1:master
into 60fa3cf on wireservice:master.

[coveralls]

coverage: 90.187% (-0.2%) from 90.393%
when pulling 278a74b on sgpeter1:master
into f73742f on wireservice:master.