Summary:
It's purpose is to illustrate that currently expansion from a single node (with a fixed degree) does not execute in consistent time, but the execution time depends on the rest of the graph (that's disconnected). Current benchmark results:
```
florijan@florxps:~/Memgraph/memgraph/build$ ./tests/benchmark/expansion
Run on (8 X 3500 MHz CPU s)
2017-08-17 16:06:30
***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
***WARNING*** Library was built as DEBUG. Timings may be affected.
Benchmark Time CPU Iterations
-------------------------------------------------------------------------
ExpansionBenchFixture/Match/1 0 ms 0 ms 4903
ExpansionBenchFixture/Match/1024 0 ms 0 ms 4785
ExpansionBenchFixture/Match/1024k 0 ms 0 ms 4623
ExpansionBenchFixture/Expand/1 9 ms 9 ms 83
ExpansionBenchFixture/Expand/1024 20 ms 20 ms 41
ExpansionBenchFixture/Expand/1024k 3430 ms 3430 ms 1
```
Reviewers: mislav.bradac, buda
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D676
