Lint on InsertLeave, not in insert mode by default

b:ale_lint_on_insert_leave is now supported as tests need it.

These defaults are saner and cause fewer issues for users by default.

doc/ale.txt

@@ -84,7 +84,7 @@ have even saved your changes. ALE will check your code in the following
 circumstances, which can be configured with the associated options.
 
 * When you modify a buffer.                - |g:ale_lint_on_text_changed|
-* On leaving insert mode. (off by default) - |g:ale_lint_on_insert_leave|
+* On leaving insert mode.                  - |g:ale_lint_on_insert_leave|
 * When you open a new or modified buffer.  - |g:ale_lint_on_enter|
 * When you save a buffer.                  - |g:ale_lint_on_save|
 * When the filetype changes for a buffer.  - |g:ale_lint_on_filetype_changed|
@@ -953,7 +953,7 @@ g:ale_lint_on_save                                         *g:ale_lint_on_save*
 g:ale_lint_on_text_changed                         *g:ale_lint_on_text_changed*
 
   Type: |String|
-  Default: `'always'`
+  Default: `'normal'`
 
   This option controls how ALE will check your files as you make changes.
   The following values can be used.
@@ -978,6 +978,7 @@ g:ale_lint_on_text_changed                         *g:ale_lint_on_text_changed*
 
 
 g:ale_lint_on_insert_leave                         *g:ale_lint_on_insert_leave*
+                                                   *b:ale_lint_on_insert_leave*
 
   Type: |Number|
   Default: `0`
@@ -992,6 +993,10 @@ g:ale_lint_on_insert_leave                         *g:ale_lint_on_insert_leave*
     " Make using Ctrl+C do the same as Escape, to trigger autocmd commands
     inoremap <C-c> <Esc>
 <
+  A buffer-local version of this setting `b:ale_lint_on_insert_leave` can be
+  set to `0` to disable linting when leaving insert mode. The setting must
+  be enabled globally to be enabled locally.
+
   You should set this setting once before ALE is loaded, and restart Vim if
   you want to change your preferences. See |ale-lint-settings-on-startup|.