Add missing "use global" var for tslint (#484)

* Add missing "use global" var for tslint
* Add typescript tslint documentation

ale_linters/typescript/tslint.vim

@@ -7,7 +7,14 @@ let g:ale_typescript_tslint_executable =
 let g:ale_typescript_tslint_config_path =
 \   get(g:, 'ale_typescript_tslint_config_path', '')
 
+let g:ale_typescript_tslint_use_global =
+\   get(g:, 'ale_typescript_tslint_use_global', 0)
+
 function! ale_linters#typescript#tslint#GetExecutable(buffer) abort
+    if ale#Var(a:buffer, 'typescript_tslint_use_global')
+        return ale#Var(a:buffer, 'typescript_tslint_executable')
+    endif
+
     return ale#path#ResolveLocalPath(
     \   a:buffer,
     \   'node_modules/.bin/tslint',

doc/ale-typescript.txt

@@ -0,0 +1,40 @@
+===============================================================================
+ALE TypeScript Integration                             *ale-typescript-options*
+
+
+-------------------------------------------------------------------------------
+tslint                                                  *ale-typescript-tslint*
+
+g:ale_typescript_tslint_executable         *g:ale_typescript_tslint_executable*
+
+  Type: |String|
+  Default: `'tslint'`
+
+  ALE will first discover the tslint path in an ancestor node_modules
+  directory. If no such path exists, this variable will be used instead.
+
+  If you wish to use only a globally installed version of tslint, set
+  |g:ale_typescript_tslint_use_global| to `1`.
+
+
+g:ale_typescript_tslint_config_path       *g:ale_typescript_tslint_config_path*
+
+  Type: |String|
+  Default: `''`
+
+  ALE will first discover the tslint.json path in an ancestor directory. If no
+  such path exists, this variable will be used instead.
+
+
+g:ale_typescript_tslint_use_global         *g:ale_typescript_tslint_use_global*
+
+  Type: |Number|
+  Default: `0`
+
+  This variable controls whether or not ALE will search for a local path for
+  tslint first. If this variable is set to `1`, then ALE will always use the
+  global version of tslint, in preference to locally installed versions of
+  tslint in node_modules.
+
+-------------------------------------------------------------------------------
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:

doc/ale.txt

@@ -74,6 +74,8 @@ CONTENTS                                                         *ale-contents*
     tex...................................|ale-tex-options|
       chktex..............................|ale-tex-chktex|
       lacheck.............................|ale-tex-lacheck|
+    typescript............................|ale-typescript-options|
+      tslint..............................|ale-typescript-tslint|
     vim...................................|ale-vim-options|
       vint................................|ale-vim-vint|
     yaml..................................|ale-yaml-options|