Adds function increment_each. This allows specifying multiple columns to increment by

[JarriqTheTechie]

Adds function increment_each. This allows specifying multiple columns to increment by

e.g.

The following will increment the users age by 5 and its children by 10.

User.find(1).increment_each([ {"age": 5}, {"children", 10} ])

the result of the action returns either model or a querybuilder

This change also rewrites the original increment function to use the new increment_each function. The function signature remains intact.

[JarriqTheTechie]

@josephmancuso please review. If this is merged I'll create a PR for decrement_each also.

[yubarajshrestha]

@JarriqTheTechie fix the conflicts.

[JarriqTheTechie]

I will work on correcting the conflicts and writing some tests this week if time permits.

[JarriqTheTechie]

Closing this PR. Will open a new one.