Remove second argument of applyChange from public api

[fedulovivan]

diff/index.js

Line 260 in c97fb9c

if (target && source && change && change.kind) {

Hello! First of all thanks for a nice tool.

Is it possible to completely remove second argument 'source' from public api of applyChange utility?
Even it is not really used (and docs clearly state this), function checks that passed source is 'truthy',
so a have to use following pattern:

changes.forEach(change => applyChange(
    INITIAL_STATE,
    true/*stated as not used in docs, but have to be truthy to pass internal checks*/, 
    change
))

My bad, got distracted and never released v1.0.0... doing that now.