Rebinding a prefix fails with SQLite

[abustany]

The current SQLite schema for binds looks like

CREATE TABLE kb_f526f39709_namespace_binds (
	prefix VARCHAR(20) NOT NULL, 
	uri TEXT, 
	PRIMARY KEY (prefix), 
	UNIQUE (prefix)
);

and the code in store.bind does (as of version 0.3.8):

ins = self.tables["namespace_binds"].insert().values(
prefix=prefix, uri=namespace)
connection.execute(ins)

which fails when rebinding a prefix, as the old prefix is not replaced...

[mwatts15]

This is resolved with the latest PR merged.