Add an option for defining text of signs

README.md

@@ -83,12 +83,22 @@ Each directory within corresponds to a particular filetype in Vim, and each file
 in each directory corresponds to the name of a particular linter.
 
 ### Always showing gutter
+
 You can keep the sign gutter open at all times by setting the g:ale_sign_column_always to 1
 
 ```vim
 let g:ale_sign_column_always = 1
 ```
 
+### Customize signs
+
+Use these options to specify what text should be used for signs:
+
+```vim
+let g:ale_sign_error = '>>'
+let g:ale_sign_warning = '--'
+```
+
 
 ## Installation