Change the behavior of skippy_node_jump() function.
Change the behavior of skippy_node_jump() function.

Now it jumps to the furthest possible node that has a key less or equal
to `target'.

yzhan018/the-day-after-tomorrow,approach0/search-engine,yzhan018/the-day-after-tomorrow,approach0/search-engine,t-k-/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,approach0/search-engine,t-k-/the-day-after-tomorrow,approach0/search-engine,t-k-/the-day-after-tomorrow