v1.5: Exchange support

Support of exchanges:
The symbol can contain an optional @eXchange field (e.g.: VIX@CBOE) which is
used to specify the exchange for the request. If not specified the exchange will be
kept on SMART as default.

Version 1.2

v1.2

BUG: Fix the returned volume. IB Returns 100s of shares

Version 1.1

v1.1

ENH: Add start and end date to filename

Initial version

v1.0

ENH: Add README.md and LICENSE to MANIFEST.in