Added change log for v0.2.0
Added change log for v0.2.0

chiefr/reactfire,carlosCeron/reactfire,StevenLangbroek/reactfire,ramyathulasingam/reactfire,Shraymonks/reactfire,ronlobo/reactfire,FirebaseExtended/reactfire,timotius02/reactfire,chiefr/reactfire,FirebaseExtended/reactfire,gragland/reactfire,Wattenberger/reactfire,FirebaseExtended/reactfire,FirebaseExtended/reactfire,Wattenberger/reactfire,StevenLangbroek/reactfire