add a delay to calls touching bref

[double-dose-larry]

to conform with Terms & Conditions of the website.

Specifically:

Except as specifically provided in this paragraph, you agree not to use or launch any automated system, including without limitation, robots, spiders, offline readers, or like devices, that accesses the Site in a manner which sends more request messages to the Site server in any given period of time than a typical human would normally produce in the same period by using a conventional on-line Web browser to read, view, and submit materials.

I suppose waiting at least a half-second is good enough. The numberize_df stuff usually takes more than that already. just want to make sure.

[double-dose-larry]

reads the page once now