Now the report shows memory peak of wt construction
Merge branch 'master' into benchmark_wt
minor cosmectic fix
Merge pull request #141 from simongog/wt_housekeeping

Wt housekeeping
Removed unused variable.
Merge pull request #142 from xosh/benchmark_wt

Benchmark wt
Fixed bug in range_search_2d
Fixed number of results in range_search_2d.
Added test for range_search_2d.
Moved quantile_freq to wt_algorithm

- moved empty(range_type) to wt_helper
- added size(range_type) operation
- moved topk_qprobing to doc_list_index_qprobing