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

autoload/ale/handlers.vim

@@ -0,0 +1,76 @@
+scriptencoding utf-8
+" Author: w0rp <devw0rp@gmail.com>
+" Description: This file defines some standard error format handlers. Any
+"   linter which outputs warnings and errors in a format accepted by one of
+"   these functions can simply use one of these pre-defined error handlers.
+
+function! ale#handlers#HandleGCCFormat(buffer, lines) abort
+    " Look for lines like the following.
+    "
+    " <stdin>:8:5: warning: conversion lacks type at end of format [-Wformat=]
+    " <stdin>:10:27: error: invalid operands to binary - (have ‘int’ and ‘char *’)
+    " -:189:7: note: $/${} is unnecessary on arithmetic variables. [SC2004]
+    let pattern = '^.\+:\(\d\+\):\(\d\+\): \([^:]\+\): \(.\+\)$'
+    let output = []
+
+    for line in a:lines
+        let l:match = matchlist(line, pattern)
+
+        if len(l:match) == 0
+            continue
+        endif
+
+        call add(output, {
+        \   'bufnr': a:buffer,
+        \   'lnum': l:match[1] + 0,
+        \   'vcol': 0,
+        \   'col': l:match[2] + 0,
+        \   'text': l:match[4],
+        \   'type': l:match[3] ==# 'error' ? 'E' : 'W',
+        \   'nr': -1,
+        \})
+    endfor
+
+    return output
+endfunction
+
+function! ale#handlers#HandleCSSLintFormat(buffer, lines) abort
+    " Matches patterns line the following:
+    "
+    " something.css: line 2, col 1, Error - Expected RBRACE at line 2, col 1. (errors)
+    " something.css: line 2, col 5, Warning - Expected (inline | block | list-item | inline-block | table | inline-table | table-row-group | table-header-group | table-footer-group | table-row | table-column-group | table-column | table-cell | table-caption | grid | inline-grid | run-in | ruby | ruby-base | ruby-text | ruby-base-container | ruby-text-container | contents | none | -moz-box | -moz-inline-block | -moz-inline-box | -moz-inline-grid | -moz-inline-stack | -moz-inline-table | -moz-grid | -moz-grid-group | -moz-grid-line | -moz-groupbox | -moz-deck | -moz-popup | -moz-stack | -moz-marker | -webkit-box | -webkit-inline-box | -ms-flexbox | -ms-inline-flexbox | flex | -webkit-flex | inline-flex | -webkit-inline-flex) but found 'wat'. (known-properties)
+    "
+    " These errors can be very massive, so the type will be moved to the front
+    " so you can actually read the error type.
+    let pattern = '^.*: line \(\d\+\), col \(\d\+\), \(Error\|Warning\) - \(.\+\) (\([^)]\+\))$'
+    let output = []
+
+    for line in a:lines
+        let l:match = matchlist(line, pattern)
+
+        if len(l:match) == 0
+            continue
+        endif
+
+        let text = l:match[4]
+        let type = l:match[3]
+        let errorGroup = l:match[5]
+
+        " Put the error group at the front, so we can see what kind of error
+        " it is on small echo lines.
+        let text = '(' . errorGroup . ') ' . text
+
+        " vcol is Needed to indicate that the column is a character.
+        call add(output, {
+        \   'bufnr': a:buffer,
+        \   'lnum': l:match[1] + 0,
+        \   'vcol': 0,
+        \   'col': l:match[2] + 0,
+        \   'text': text,
+        \   'type': type ==# 'Warning' ? 'W' : 'E',
+        \   'nr': -1,
+        \})
+    endfor
+
+    return output
+endfunction