Doesn't work with WP 4.9.4

[zrubinrattet]

Since WP 4.9.4 is now hashing their value in the search param when building the query this script would need to be rebuilt to support that.

[mariovalney]

Probably it happens because the change in esc_sql() in version *4.8.3.
More details: https://make.wordpress.org/core/2017/10/31/changed-behaviour-of-esc_sql-in-wordpress-4-8-3/

In line 71 and 72 the class spects to find LIKE '%{$s}% but we have a placeholder escape in place.

[mariovalney]

Please, check this fix: #27