Add support for npm-groovy-lint (#4495)

* Add support for npm-groovy-lint

* Add doc and tests for npm-groovy-lint

* Use ale#util#FuzzyJSONDecode instead of json_decode

doc/ale-groovy.txt

@@ -0,0 +1,42 @@
+===============================================================================
+ALE Groovy Integration                                     *ale-groovy-options*
+
+
+===============================================================================
+Integration Information
+
+Linting and fixing of Groovy files is enabled with the integration of
+`npm-groovy-lint`.
+
+
+===============================================================================
+npm-groovy-lint                                    *ale-groovy-npm-groovy-lint*
+
+g:ale_groovy_npmgroovylint_executable   *g:ale_groovy_npmgroovylint_executable*
+                                        *b:ale_groovy_npmgroovylint_executable*
+  Type: |String|
+  Default: `'npm-groovy-lint'`
+
+  Location of the npm-groovy-lint binary file.
+
+
+g:ale_groovy_npmgroovylint_options         *g:ale_groovy_npmgroovylint_options*
+                                           *b:ale_groovy_npmgroovylint_options*
+  Type: |String|
+  Default: `'--loglevel warning'`
+
+  Additional npm-groovy-lint linter options.
+
+
+g:ale_groovy_npmgroovylint_fix_options *g:ale_groovy_npmgroovylint_fix_options*
+                                       *b:ale_groovy_npmgroovylint_fix_options*
+  Type: |String|
+  Default: `'--fix'`
+
+  This variable can be used to configure fixing with npm-groovy-lint. It must
+  contain either `--fix` or `--format` for the fixer to work. See
+  `npm-groovy-lint --help` for more information on possible fix rules.
+
+
+===============================================================================
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl: