Adds Support to Mini VIX (VXM) Futures

[AlexCatarino]

Expected Behavior

Support VIX Mini Futures.

Actual Behavior

Not supported.

Potential Solution

See contract specifications on: https://cdn.cboe.com/resources/futures/VXM_Contract_Specifications.pdf

Checklist

• [x] I have completely filled out this template
• [x] I have confirmed that this issue exists on the current master branch
• [x] I have confirmed that this is not a duplicate issue by searching issues
• [x] I have provided detailed steps to reproduce the issue

[marcokrueger]

Please implement this. VX is too big for most accounts. Should be easy to support as it's just 1/10th of VX