Moved rules into their own files

Everything under `lib/rules/*` is a rules file (with the name of the rule in camelCase), re-exported into an array in `lib/rules.js`.
Moved the regular expressions from `lib/rules.js` to `lib/expressions.js`, and the rest of the variables into `lib/shared.js`.

lib/rules/noTrailingSpaces.js

@@ -0,0 +1,33 @@
+var shared = require("../shared");
+var expressions = require("../expressions");
+
+module.exports = {
+  "name": "MD009",
+  "desc": "Trailing spaces",
+  "tags": [ "whitespace" ],
+  "aliases": [ "no-trailing-spaces" ],
+  "regexp": expressions.trailingSpaceRe,
+  "func": function MD009(params, errors) {
+    var brSpaces = params.options.br_spaces || 0;
+    var listItemEmptyLines = params.options.list_item_empty_lines;
+    var allowListItemEmptyLines =
+      (listItemEmptyLines === undefined) ? false : !!listItemEmptyLines;
+    var listItemLineNumbers = [];
+    if (allowListItemEmptyLines) {
+      shared.filterTokens(params, "list_item_open", function forToken(token) {
+        for (var i = token.map[0]; i < token.map[1]; i++) {
+          listItemLineNumbers.push(i + 1);
+        }
+      });
+    }
+    shared.forEachLine(params, function forLine(line, lineIndex) {
+      var lineNumber = lineIndex + 1;
+      if (expressions.trailingSpaceRe.test(line) &&
+        (listItemLineNumbers.indexOf(lineNumber) === -1)) {
+        var expected = (brSpaces < 2) ? 0 : brSpaces;
+        errors.addDetailIf(lineNumber,
+          expected, line.length - line.trimRight().length);
+      }
+    });
+  }
+};