implement migrate:fresh

[eaguad1337]

Implements #860

I tested it on MySQL, SQLite and Postgres because I had problems running tests. Hopefully you can help me with this tests @josephmancuso

[josephmancuso]

i just spent a good amount of time trying to get this to work ecause my tables all had foreign key constraints with eachother

[eaguad1337]

i just spent a good amount of time trying to get this to work ecause my tables all had foreign key constraints with eachother

I added a ignore_fk param and I realized that Postgres fails when trying to use enable_foreign_key_constraints because this method is not implemented. I returned true if sql is None. Let me know if makes sense to you.

[josephmancuso]

hmm now these tests are failing

[eaguad1337]

removed workaround for not implemented methods in mssql and postgres @josephmancuso

[yubarajshrestha]

@eaguad1337 please fix the linter issues, I believe it's good to have this feature in the framework.

[josephmancuso]

LGTM