Adapter postgres url scheme

[baoyachi]

working for #200

• adapter postgres url scheme
• add new method in DbBackend with name url_starts_with.

[tyt2y3]

Thank you so much for this. I think my only nitpick would be to think of a better name for the method url_starts_with.
Because in left to right order, url starts with mysql makes sense.
But in reverse, mysql starts with url does not.
May be, I suggest, to use is_prefix_of as in mysql is prefix of url.
Sounds good?

[baoyachi]

Thank you so much for this. I think my only nitpick would be to think of a better name for the method url_starts_with.
Because in left to right order, url starts with mysql makes sense.
But in reverse, mysql starts with url does not.
May be, I suggest, to use is_prefix_of as in mysql is prefix of url.
Sounds good?

Done.

[tyt2y3]

Awesome!