v1.4.0

ModelingToolkitStandardLibrary v1.4.0

Diff since v1.3.1

Merged pull requests:

• Define Voltage, Current (#51) (@ven-k)
• add missing link to tutorial (#63) (@ValentinKaisermayer)
• Electrical formatting changes (#64) (@ValentinKaisermayer)
• adds return code checks (#65) (@ValentinKaisermayer)
• Add Short in Analog and TwoPort in Electrical (#66) (@ven-k)
• Fix matrix gain for vectors (#67) (@baggepinnen)
• add duration keyword to step (#68) (@baggepinnen)
• Patch blocks (#69) (@ValentinKaisermayer)