Add gte and lte, and add criterion based query building.

[mvanderlee]

I really like the pypika query builder, so implemented a similar method.

Allows things like:

incident = Table('incident')
criterion_list = [
    Field('foo').eq('bar'), 
    incident.bar == 'foo'
]
query = str(reduce(operator.and_, criterion_list))
print(query)

>>> 'foo=bar^bar=foo'

print(str(Field('foo').eq('bar') | incident.bar == 'foo'))

>>> 'foo=bar^ORbar=foo'

[rbw]

Looks like a nice feature! I'll take a look and test it out this weekend.

[rbw]

I've looked through the code and done some basic testing, and it works really well.

I'll do some more testing during the coming week and have it incorporated into pysnow as soon as possible.

Big thanks!

[mvanderlee]

Great :) thanks