First pass at optimizing ale to autoload (#80)

* First pass at optimizing ale to autoload

First off, the structure/function names should be revised a bit,
but I will wait for @w0rp's input before unifying the naming style.
Second off, the docs probably need some more work, I just did some
simple find-and-replace work.

With that said, this pull brings major performance gains for ale. On my
slowest system, fully loading ale and all its code takes around 150ms.

I have moved all of ale's autoload-able code to autoload/, and in
addition, implemented lazy-loading of linters. This brings load time on
that same system down to 5ms.

The only downside of lazy loading is that `g:ale_linters` cannot be
changed at runtime; however, it also speeds up performance at runtime by
simplfying the logic greatly.

Please let me know what you think!

Closes #59

* Address Travis/Vint errors

For some reason, ale isn't running vint for me...

* Incorporate feedback, make fixes

Lazy-loading logic is much improved.

* Add header comments; remove incorrect workaround

* Remove unneeded plugin guards

* Fix lazy-loading linter logic

Set the wrong variable....

* Fix capitialization

ale_linters/javascript/eslint.vim

@@ -49,14 +49,14 @@ function! ale_linters#javascript#eslint#Handle(buffer, lines)
     return output
 endfunction
 
-call ALEAddLinter('javascript', {
+call ale#linter#Define('javascript', {
 \   'name': 'eslint',
 \   'executable': g:ale_javascript_eslint_executable,
 \   'command': g:ale_javascript_eslint_executable . ' -f unix --stdin --stdin-filename %s',
 \   'callback': 'ale_linters#javascript#eslint#Handle',
 \})
 
-call ALEAddLinter('javascript.jsx', {
+call ale#linter#Define('javascript.jsx', {
 \   'name': 'eslint',
 \   'executable': g:ale_javascript_eslint_executable,
 \   'command': g:ale_javascript_eslint_executable . ' -f unix --stdin --stdin-filename %s',

ale_linters/javascript/jscs.vim

@@ -43,14 +43,14 @@ function! ale_linters#javascript#jscs#Handle(buffer, lines)
     return output
 endfunction
 
-call ALEAddLinter('javascript', {
+call ale#linter#Define('javascript', {
 \   'name': 'jscs',
 \   'executable': 'jscs',
 \   'command': 'jscs -r unix -n -',
 \   'callback': 'ale_linters#javascript#jscs#Handle',
 \})
 
-call ALEAddLinter('javascript.jsx', {
+call ale#linter#Define('javascript.jsx', {
 \   'name': 'jscs',
 \   'executable': 'jscs',
 \   'command': 'jscs -r unix -n -',

ale_linters/javascript/jshint.vim

@@ -70,14 +70,14 @@ function! ale_linters#javascript#jshint#Handle(buffer, lines)
     return output
 endfunction
 
-call ALEAddLinter('javascript', {
+call ale#linter#Define('javascript', {
 \   'name': 'jshint',
 \   'executable': g:ale_javascript_jshint_executable,
 \   'command_callback': 'ale_linters#javascript#jshint#GetCommand',
 \   'callback': 'ale_linters#javascript#jshint#Handle',
 \})
 
-call ALEAddLinter('javascript.jsx', {
+call ale#linter#Define('javascript.jsx', {
 \   'name': 'jshint',
 \   'executable': g:ale_javascript_jshint_executable,
 \   'command_callback': 'ale_linters#javascript#jshint#GetCommand',