v0.1.20

ITensors v0.1.20

Diff since v0.1.19

Closed issues:

• Add CompatHelper (#371)
• Use a Dict to store op definitions (#375)

Merged pull requests:

• Add QN ITensor from Array constructor (#464) (@mtfishman)
• Introduce filterinds (#466) (@mtfishman)
• Make ITensors compatible with Julia v1.3 (#468) (@mtfishman)