preserve_sqlite_parameters

[stonebig]

Hello Greg,

its seems 'pandsql' omits to send parameters to sqlite motor, which would be nice to have.
Here is a separate fix proposal, and associated test.

mylist = [ ('a',1), ('b', 2)]
myanswer=42
result = sqldf("SELECT *, :myanswer FROM mylist",locals())
print (result)

[stonebig]

Yes, you're absolutely right. I discovered it later.
"def sqldf(q, env, inmemory=True): " is a better option.

[stonebig]

The other on-liner of the patch, and the associated test, was the important point to get sqlite ":variable" way of parametrizing working.