Rename startKey() into setStartKey() to be consistent with the naming convention

Hello @dpup, 

Please review the following commits I made in branch 'xiao-setStartKey'.

e686fffe35cacb68e9c9a6d0718498d9658eb188 (2013-10-14 16:36:42 -0700)
Rename startKey() into setStartKey() to be consistent with the naming convention

Check list:


R=@dpup