Removed syntastic and replaced it with ale

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

sources_non_forked/ale/ale_linters/java/checkstyle.vim

@@ -0,0 +1,36 @@
+" Author: Devon Meunier <devon.meunier@gmail.com>
+" Description: checkstyle for Java files
+
+function! ale_linters#java#checkstyle#Handle(buffer, lines) abort
+    let l:pattern = '\v\[(WARN|ERROR)\] [a-zA-Z]?:?[^:]+:(\d+):(\d+)?:? (.*) \[(.+)\]$'
+    let l:output = []
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        call add(l:output, {
+        \   'type': l:match[1] is? 'WARN' ? 'W' : 'E',
+        \   'lnum': l:match[2] + 0,
+        \   'col': l:match[3] + 0,
+        \   'text': l:match[4],
+        \   'code': l:match[5],
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+function! ale_linters#java#checkstyle#GetCommand(buffer) abort
+    return 'checkstyle '
+    \ . ale#Var(a:buffer, 'java_checkstyle_options')
+    \ . ' %t'
+endfunction
+
+if !exists('g:ale_java_checkstyle_options')
+    let g:ale_java_checkstyle_options = '-c /google_checks.xml'
+endif
+
+call ale#linter#Define('java', {
+\   'name': 'checkstyle',
+\   'executable': 'checkstyle',
+\   'command_callback': 'ale_linters#java#checkstyle#GetCommand',
+\   'callback': 'ale_linters#java#checkstyle#Handle',
+\})