BUG: Fix pandas.io.data.Options for change in format of Yahoo Option page

ENH: Automatically choose next expiry if expiry date isn't valid

COMPAT: Remove dictionary comprehension to pass 2.6 test

BUG: Add check that tables were downloaded.

ENH: Replace third_saturday function with Pandas offset

BUG: Check to make sure enough option tables are downloaded.

TST: Add sample options page during market open.

DOC: Add bug fix report to v0.15.1.txt for data.Options