specifing unit measure in readme

Author: san4io

README.md

@@ -398,7 +398,7 @@ whereNotBetween($field, $value) | whereNotBetween('price', [100, 200]) | Checks
 whereExists($field) | whereExists('unemployed') | Checks if a value is defined.
 whereNotExists($field) | whereNotExists('unemployed') | Checks if a value isn't defined.  
 whereRegexp($field, $value, $flags = 'ALL') | whereRegexp('name.raw', 'A.+') | Filters records according to a given regular expression. [Here](https://www.elastic.co/guide/en/elasticsearch/reference/5.2/query-dsl-regexp-query.html#regexp-syntax) you can find more about syntax.
-whereGeoDistance($field, $value, $distance) | whereGeoDistance('location', [-70, 40], 1000) | Filters records according to given point and distance from it. [Here](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-geo-distance-query.html) you can find more about syntax.
+whereGeoDistance($field, $value, $distance) | whereGeoDistance('location', [-70, 40], '1000m') | Filters records according to given point and distance from it. [Here](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-geo-distance-query.html) you can find more about syntax.
 whereGeoBoundingBox($field, array $value) | whereGeoBoundingBox('location', ['top_left' =>  [-74.1, 40.73], 'bottom_right' => [-71.12, 40.01]]) | Filters records within given boundings. [Here](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-geo-bounding-box-query.html) you can find more about syntax.
 whereGeoPolygon($field, array $points) | whereGeoPolygon('location', [[-70, 40],[-80, 30],[-90, 20]]) | Filters records within given polygon. [Here](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-geo-polygon-query.html) you can find more about syntax.