Implement Lua ALE setup & overhaul documentation

1. Add ale.setup and ale.setup.buffer for pure Lua configuration.
2. Update many global settings to use Booleans instead of numbers to
   make types easiert to work with in Lua.
3. Radically reformat documentation and fix errors to make
   documentation more usable for Neovim users.

test/completion/test_ale_import_command.vader

@@ -92,6 +92,12 @@ Before:
     call g:LastHandleCallback(a:conn_id, a:message)
     AssertEqual [[0, '']], g:ale_queue_call_list
 
+    let g:ale_lint_on_text_changed = v:true
+
+    let g:ale_queue_call_list = []
+    call g:LastHandleCallback(a:conn_id, a:message)
+    AssertEqual [[0, '']], g:ale_queue_call_list
+
     let g:ale_lint_on_text_changed = 'normal'
 
     let g:ale_queue_call_list = []
@@ -228,7 +234,7 @@ Execute(ALEImport should request imports correctly for tsserver):
   \ [
   \   [0, 'ts@completions', {
   \     'file': expand('%:p'),
-  \     'includeExternalModuleExports': 1,
+  \     'includeExternalModuleExports': v:true,
   \     'offset': 21,
   \     'line': 2,
   \     'prefix': 'missingword',

test/completion/test_lsp_completion_messages.vader

@@ -1,11 +1,14 @@
 Before:
   Save g:ale_completion_delay
+  Save g:ale_completion_enabled
   Save g:ale_completion_max_suggestions
   Save g:ale_completion_info
+  Save g:ale_completion_autoimport
   Save &l:omnifunc
   Save &l:completeopt
 
-  let g:ale_completion_enabled = 1
+  let g:ale_completion_enabled = v:true
+  let g:ale_completion_autoimport = v:true
 
   call ale#test#SetDirectory('/testplugin/test/completion')
   call ale#test#SetFilename('dummy.txt')

test/completion/test_tsserver_completion_parsing.vader

@@ -1,7 +1,9 @@
 Before:
+  Save g:ale_completion_autoimport
   Save g:ale_completion_tsserver_remove_warnings
 
-  let g:ale_completion_tsserver_remove_warnings = 0
+  let g:ale_completion_autoimport = v:true
+  let g:ale_completion_tsserver_remove_warnings = v:false
 
 After:
   Restore
@@ -91,7 +93,7 @@ Execute(TypeScript completion details responses should be parsed correctly):
   \     'kind': 'v',
   \     'icase': 1,
   \     'user_data': json_encode({'_ale_completion_item': 1}),
-  \     'dup': g:ale_completion_autoimport,
+  \     'dup': g:ale_completion_autoimport + 0,
   \   },
   \   {
   \     'word': 'def',
@@ -100,7 +102,7 @@ Execute(TypeScript completion details responses should be parsed correctly):
   \     'kind': 'v',
   \     'icase': 1,
   \     'user_data': json_encode({'_ale_completion_item': 1}),
-  \     'dup': g:ale_completion_autoimport,
+  \     'dup': g:ale_completion_autoimport + 0,
   \   },
   \   {
   \     'word': 'ghi',
@@ -109,7 +111,7 @@ Execute(TypeScript completion details responses should be parsed correctly):
   \     'kind': 'v',
   \     'icase': 1,
   \     'user_data': json_encode({'_ale_completion_item': 1}),
-  \     'dup': g:ale_completion_autoimport,
+  \     'dup': g:ale_completion_autoimport + 0,
   \   },
   \ ],
   \ ale#completion#ParseTSServerCompletionEntryDetails({
@@ -188,7 +190,7 @@ Execute(Entries without details should be included in the responses):
   \             'changes': [],
   \         }],
   \     }),
-  \     'dup': g:ale_completion_autoimport,
+  \     'dup': g:ale_completion_autoimport + 0,
   \   },
   \   {
   \     'word': 'def',
@@ -197,7 +199,7 @@ Execute(Entries without details should be included in the responses):
   \     'kind': 'v',
   \     'icase': 1,
   \     'user_data': json_encode({'_ale_completion_item': 1}),
-  \     'dup': g:ale_completion_autoimport,
+  \     'dup': g:ale_completion_autoimport + 0,
   \   },
   \   {
   \     'word': 'xyz',
@@ -272,7 +274,7 @@ Execute(Default imports should be handled correctly):
   \             'changes': [],
   \         }],
   \     }),
-  \     'dup': g:ale_completion_autoimport,
+  \     'dup': g:ale_completion_autoimport + 0,
   \   },
   \ ],
   \ ale#completion#ParseTSServerCompletionEntryDetails({