Rename "refinery_schema_history" to something starting with __

[omid]

To be compatible with diesel print-schema command, I would suggest we can rename the migration table to something else which starts with __ (a double underscore).

[jxs]

hum, what is the advantage with this? Don't diesel and refinery kinda overlap? My issue with this is the same with changing the type on the version column: a breaking change that envolves manually renaming a table. For this I would prefer we actually go for #109 with the default being refinery_schema_history

[omid]

There is an overlap between diesel_migrations and refinery.
There are some overlaps between refinery_cli and diesel_cli.

diesel cli can generate the schema.rs file, which is kinda required if you want to use diesel.

And diesel will skip tables that starts with __ in the schema.

[jxs]

addressed with #207