Test: cache size test clarified
Cache: syncset and timeset were merged into eventset to save memory
Cache: treap implementation added
Cache: Treap refactored. Set replaced with treap in slru_cache.
Cache: bug with default 0 eventtime fixed.
Cache: decrease key optimization added to avoid unnecessary
erases/inserts in treap
Cache: cache_pages_proportions added to config. Stats for each cache
page added
Merge branch 'master' of https://github.com/reverbrain/elliptics into cache_treap

Merge conflicts resolved
Merge pull request #286 from IIoTeP9HuY/cache_treap

Cache treap