Aqueduct-client

We've added an example notebook and an example pipeline query.

Also, some internal (non-client-facing) improvements.

ENH: Update to add link to live QE docs

ENH: Update asset_identifier_format default to sid

asset_identifier_format values of `symbol` and `fsym_region_id` are _only valid_ for US_EQUITIES domains.

`symbol` will cause a `TypeError: Expected unicode, got <type 'str'>` exception, while `fsym_region_id` will cause `IndexError: cannot do a non-empty take from an empty axes.`

Adds support for checking for the concurrent execution limit.

Adds Versioneer support, to better support versioning and future upgrades.