Prefer --fast for stack-build (#754)

* Vim scripts shouldn't have hyphens

Especially not ones that will be autoloaded. You can't have a hyphen in
a function name, so autoloading functions based on filename will fail.

* Add g:haskell_stack_build_options, default: --fast

If we're going to use the --fast option, we may as well go the whole 9
yards and let the user configure the 'stack build' flags.

* Create documentation for stack-build options

ale_linters/haskell/stack_ghc.vim

@@ -0,0 +1,10 @@
+" Author: w0rp <devw0rp@gmail.com>
+" Description: ghc for Haskell files, using Stack
+
+call ale#linter#Define('haskell', {
+\   'name': 'stack-ghc',
+\   'output_stream': 'stderr',
+\   'executable': 'stack',
+\   'command': 'stack ghc -- -fno-code -v0 %t',
+\   'callback': 'ale#handlers#haskell#HandleGHCFormat',
+\})