Fix binary search

[MaximSmolskiy]

Current binary search implementation has bug. For example,

>> binary_search(1:100, 30)
target is not found in aray

>> binary_search(1:100, 70)
target is not found in aray

The bug is in maximum iteration needed to find the target. There should be binary logarithm log2 instead of natural log. In case of natural logarithm log algorithm lacks iterations in some cases (e.g. in above). But in some cases it works properly. For example,

>> binary_search(1:100, 50)

ans =

    50

[cozek]

Thanks!