Update readme with correct groovy version and fix raster groovydocs

Author: jericks

README.rst

@@ -135,7 +135,7 @@ Versions
 +-----------+----------+-----------+--------+----------+
 | GeoScript | GeoTools | GeoServer | JTS    | Groovy   |
 +-----------+----------+-----------+--------+----------+
-| 1.13      | 21       | 2.15      | 1.16.0 | 2.5.5    |
+| 1.13      | 21       | 2.15      | 1.16.0 | 2.5.6    |
 +-----------+----------+-----------+--------+----------+
 | 1.12      | 20       | 2.14      | 1.16.0 | 2.4.15   |
 +-----------+----------+-----------+--------+----------+

src/main/groovy/geoscript/layer/Raster.groovy

@@ -890,7 +890,7 @@ class Raster implements Renderable {
 
     /**
      * Calculate a convoluted version of the current Raster
-     * @param options Optional named parameters (kernel, kernelRadius, kernelWidth and kernelHeight)
+     * @param radius The kernel radius
      * @return A Raster
      */
     Raster convolve(int radius) {
@@ -901,7 +901,8 @@ class Raster implements Renderable {
 
     /**
      * Calculate a convoluted version of the current Raster
-     * @param options Optional named parameters (kernel, kernelRadius, kernelWidth and kernelHeight)
+     * @param width The kernel width
+     * @param height The height width
      * @return A Raster
      */
     Raster convolve(int width, int height) {