Removed syntastic and replaced it with ale

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

sources_non_forked/ale/ale_linters/crystal/crystal.vim

@@ -0,0 +1,31 @@
+" Author: Jordan Andree <https://github.com/jordanandree>, David Alexander <opensource@thelonelyghost.com>
+" Description: This file adds support for checking Crystal with crystal build
+
+function! ale_linters#crystal#crystal#Handle(buffer, lines) abort
+    let l:output = []
+
+    for l:error in ale#util#FuzzyJSONDecode(a:lines, [])
+        call add(l:output, {
+        \   'lnum': l:error.line + 0,
+        \   'col': l:error.column + 0,
+        \   'text': l:error.message,
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+function! ale_linters#crystal#crystal#GetCommand(buffer) abort
+    return 'crystal build -f json --no-codegen --no-color -o '
+    \   . ale#Escape(g:ale#util#nul_file)
+    \   . ' %s'
+endfunction
+
+call ale#linter#Define('crystal', {
+\   'name': 'crystal',
+\   'executable': 'crystal',
+\   'output_stream': 'both',
+\   'lint_file': 1,
+\   'command_callback': 'ale_linters#crystal#crystal#GetCommand',
+\   'callback': 'ale_linters#crystal#crystal#Handle',
+\})