Change TreeSitterLanguageMode::bufferRangeForScopeAtPosition(position) to

bufferRangeForScopeAtPosition(selector, position), to match the TextMateLanguageMode
signature, extracting some selector matching logic to do so.

Needed for https://github.com/atom/toggle-quotes/issues/57

src/selectors.js

@@ -0,0 +1,42 @@
+module.exports = {selectorMatchesAnyScope, matcherForSelector}
+
+const _ = require('underscore-plus')
+
+/**
+ * Parse a selector into parts. If already parsed, returns the selector
+ * unmodified.
+ * 
+ * @param {String|Array<String>} selector
+ * @returns {Array<String>} selector parts
+ */
+function parse (selector) {
+  return typeof selector === 'string'
+    ? selector.replace(/^\./, '').split('.')
+    : selector
+}
+
+const always = scope => true
+
+/**
+ * Return a matcher function for a selector.
+ * 
+ * @param {String} selector
+ * @returns {(scope: String) -> Boolean} a matcher function
+ */
+function matcherForSelector (selector) {
+  const parts = parse(selector)
+  return selector
+    ? scope => _.isSubset(parts, parse(scope))
+    : always
+}
+
+/**
+ * Return true iff the selector matches any provided scope.
+ * 
+ * @param {String} selector
+ * @param {Array<String>} scopes
+ * @returns {Boolean} true if any scope matches the selector
+ */
+function selectorMatchesAnyScope (selector, scopes) {
+  return !selector || scopes.some(matcherForSelector(selector))
+}