Hygiene: upgrade Gradle to v2.6
Hygiene: upgrade Gradle to v2.6

Change-Id: I6b096abdcb1fc549aa712d2fabc56bd9f1d667bb

anirudh24seven/apps-android-wikipedia,parvez3019/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,parvez3019/apps-android-wikipedia,parvez3019/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,dbrant/apps-android-wikipedia,wikimedia/apps-android-wikipedia,parvez3019/apps-android-wikipedia,carloshwa/apps-android-wikipedia,carloshwa/apps-android-wikipedia,wikimedia/apps-android-wikipedia,dbrant/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,dbrant/apps-android-wikipedia,Duct-and-rice/KrswtkhrWiki4Android,parvez3019/apps-android-wikipedia,wikimedia/apps-android-wikipedia,Duct-and-rice/KrswtkhrWiki4Android,carloshwa/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,dbrant/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,Duct-and-rice/KrswtkhrWiki4Android,wikimedia/apps-android-wikipedia,Duct-and-rice/KrswtkhrWiki4Android,Wikinaut/wikipedia-app,carloshwa/apps-android-wikipedia,Duct-and-rice/KrswtkhrWiki4Android,Wikinaut/wikipedia-app,SAGROUP2/apps-android-wikipedia,Wikinaut/wikipedia-app,dbrant/apps-android-wikipedia,carloshwa/apps-android-wikipedia,Wikinaut/wikipedia-app,Wikinaut/wikipedia-app