Blayne V

Closes #49 - all tests added / passed ``` >>> import pdblp >>> con = pdblp.BCon(port=8194, timeout=5000) >>> con.start() >>> con.secf("IBM") ticker description 0 IBM US EQUITY International Business Machines...

Implementation of the terminal function "SECF" which allows query based lookup of tickers using a search string. This leverages the "instruments" service using the `InstrumentListRequest ` request type. I can...