Update requirements.txt

[xanderstevenson]

Users will need to install several libraries to get this learning lab to run"

https://developer.cisco.com/learning/tracks/aci-programmability/intro-to-aci/sbx-intro-aci-03_aci-toolkit/introduction/

best to just install them at the beginning so new users aren't confused.

This is a judgement call...not a 'necessary' update but 'helpful'

[agentlecisco]

Holy cow that's a longer list :)