Make it easier to run tests locally

Certain tests could break if you ran them separately from other tests.
They have been patched.

`run-tests` now has a `--fast` option which runs tests with only the
fastest Vim version ALE tests with, and the custom checks.

test/lsp/test_lsp_command_formatting.vader

@@ -1,6 +1,10 @@
 Before:
+  Save g:ale_command_wrapper
+
   runtime autoload/ale/lsp.vim
 
+  let g:ale_command_wrapper = ''
+
   let g:args = []
 
   " Mock the StartProgram function so we can just capture the arguments.
@@ -9,6 +13,8 @@ Before:
   endfunction
 
 After:
+  Restore
+
   unlet! g:args
 
   runtime autoload/ale/lsp.vim