Removed syntastic and replaced it with ale

Read more here:
https://github.com/w0rp/ale

sources_non_forked/ale/ale_linters/sh/shell.vim

@@ -0,0 +1,57 @@
+" Author: w0rp <devw0rp@gmail.com>
+" Description: Lints sh files using bash -n
+
+" Backwards compatibility
+if exists('g:ale_linters_sh_shell_default_shell')
+    let g:ale_sh_shell_default_shell = g:ale_linters_sh_shell_default_shell
+endif
+
+" This option can be changed to change the default shell when the shell
+" cannot be taken from the hashbang line.
+if !exists('g:ale_sh_shell_default_shell')
+    let g:ale_sh_shell_default_shell = fnamemodify($SHELL, ':t')
+
+    if g:ale_sh_shell_default_shell is# '' || g:ale_sh_shell_default_shell is# 'fish'
+        let g:ale_sh_shell_default_shell = 'bash'
+    endif
+endif
+
+function! ale_linters#sh#shell#GetExecutable(buffer) abort
+    let l:shell_type = ale#handlers#sh#GetShellType(a:buffer)
+
+    if !empty(l:shell_type)
+        return l:shell_type
+    endif
+
+    return ale#Var(a:buffer, 'sh_shell_default_shell')
+endfunction
+
+function! ale_linters#sh#shell#GetCommand(buffer) abort
+    return ale_linters#sh#shell#GetExecutable(a:buffer) . ' -n %t'
+endfunction
+
+function! ale_linters#sh#shell#Handle(buffer, lines) abort
+    " Matches patterns line the following:
+    "
+    " bash: line 13: syntax error near unexpected token `d'
+    " sh: 11: Syntax error: "(" unexpected
+    let l:pattern = '\v(line |: ?)(\d+): (.+)$'
+    let l:output = []
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        call add(l:output, {
+        \   'lnum': str2nr(l:match[2]),
+        \   'text': l:match[3],
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+call ale#linter#Define('sh', {
+\   'name': 'shell',
+\   'output_stream': 'stderr',
+\   'executable_callback': 'ale_linters#sh#shell#GetExecutable',
+\   'command_callback': 'ale_linters#sh#shell#GetCommand',
+\   'callback': 'ale_linters#sh#shell#Handle',
+\})