Add options to facilitate linting only in normal mode (#425)

* [#420] Add options to facilitate linting only in normal mode

ale_lint_on_text_changed:
Allow setting to 'insert' or 'normal' to lint when text is changed only in
insert or normal mode respectively.

ale_lint_on_insert_leave:
This flag can be set to 1 to enable linting when leaving insert mode.

* [#420] Test updated global options

Ale should
- bind to TextChanged events when g:ale_lint_on_text_changed = 1
- bind to TextChanged events when g:ale_lint_on_text_changed = 'always'
- bind to InsertLeave event when g:ale_lint_on_insert_leave = 1

test/test_ale_info.vader

@@ -19,7 +19,7 @@ Before:
   \  'let g:ale_lint_delay = 200',
   \  'let g:ale_lint_on_enter = 1',
   \  'let g:ale_lint_on_save = 1',
-  \  'let g:ale_lint_on_text_changed = 1',
+  \  'let g:ale_lint_on_text_changed = ''always''',
   \  'let g:ale_linter_aliases = {}',
   \  'let g:ale_linters = {}',
   \  'let g:ale_open_list = 0',

test/test_ale_init_au_groups.vader

@@ -0,0 +1,66 @@
+Before:
+  Save g:ale_lint_on_text_changed
+  Save g:ale_lint_on_insert_leave
+  autocmd!
+
+After:
+  Restore g:ale_lint_on_text_changed
+  Restore g:ale_lint_on_insert_leave
+  unlet! g:output
+  unlet! g:expected_autocmd
+  autocmd!
+
+Execute (ALE should bind to TextChanged events when g:ale_lint_on_text_changed = 1):
+  let g:expected_autocmd = join([
+  \  '',
+  \  '--- Auto-Commands ---',
+  \  'ALERunOnTextChangedGroup  TextChanged',
+  \  '    *         call ale#Queue(g:ale_lint_delay)',
+  \  'ALERunOnTextChangedGroup  TextChangedI',
+  \  '    *         call ale#Queue(g:ale_lint_delay)',
+  \], "\n")
+
+  let g:ale_lint_on_text_changed = 1
+  call ALEInitAuGroups()
+
+  redir => g:output
+  autocmd ALERunOnTextChangedGroup TextChanged,TextChangedI *
+  redir END
+
+  AssertEqual g:expected_autocmd, g:output
+
+Execute (ALE should bind to TextChanged events when g:ale_lint_on_text_changed = 'always'):
+  let g:expected_autocmd = join([
+  \  '',
+  \  '--- Auto-Commands ---',
+  \  'ALERunOnTextChangedGroup  TextChanged',
+  \  '    *         call ale#Queue(g:ale_lint_delay)',
+  \  'ALERunOnTextChangedGroup  TextChangedI',
+  \  '    *         call ale#Queue(g:ale_lint_delay)',
+  \], "\n")
+
+  let g:ale_lint_on_text_changed = 'always'
+  call ALEInitAuGroups()
+
+  redir => g:output
+  autocmd ALERunOnTextChangedGroup TextChanged,TextChangedI *
+  redir END
+
+  AssertEqual g:expected_autocmd, g:output
+
+Execute (ALE should bind to InsertLeave event when g:ale_lint_on_insert_leave = 1):
+  let g:expected_autocmd = join([
+  \  "",
+  \  "--- Auto-Commands ---",
+  \  "ALERunOnInsertLeave  InsertLeave",
+  \  "    *         call ale#Queue(0, 'lint_file')",
+  \], "\n")
+
+  let g:ale_lint_on_insert_leave = 1
+  call ALEInitAuGroups()
+
+  redir => g:output
+  autocmd ALERunOnInsertLeave InsertLeave *
+  redir END
+
+  AssertEqual g:expected_autocmd, g:output