Fix vulnerable dependencies

[jnikles]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) Update lodash dependency due to npm audit warnings. Had to adjust .each loops primarily, since binding is not support in anymore 4.x, using arrow functions instead.

• What is the current behavior? (You can also link to an open issue here) Gekko runs correctly

• What is the new behavior (if this is a feature change)? no new behavior introduced. Tests pass

• Other information:

• introduce arrow functions in _.each

• replace .first(, ) with .slice

• adjust variable names here an there

[jnikles]

have to do some manual checks on top before this is ready