Removed syntastic and replaced it with ale

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

sources_non_forked/ale/ale_linters/pony/ponyc.vim

@@ -0,0 +1,21 @@
+" Description: ponyc linter for pony files
+
+call ale#Set('pony_ponyc_executable', 'ponyc')
+call ale#Set('pony_ponyc_options', '--pass paint')
+
+function! ale_linters#pony#ponyc#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'pony_ponyc_executable')
+endfunction
+
+function! ale_linters#pony#ponyc#GetCommand(buffer) abort
+    return ale#Escape(ale_linters#pony#ponyc#GetExecutable(a:buffer))
+    \   . ' ' . ale#Var(a:buffer, 'pony_ponyc_options')
+endfunction
+
+call ale#linter#Define('pony', {
+\   'name': 'ponyc',
+\   'output_stream': 'stderr',
+\   'executable_callback': 'ale_linters#pony#ponyc#GetExecutable',
+\   'command_callback': 'ale_linters#pony#ponyc#GetCommand',
+\   'callback': 'ale#handlers#pony#HandlePonycFormat',
+\})