Update R.sortBy to accept Ord, per documentation

http://ramdajs.com/docs/#sortBy

types/ramda/index.d.ts

@@ -1,6 +1,6 @@
 // Type definitions for ramda
 // Project: https://github.com/donnut/typescript-ramda
-// Definitions by: Erwin Poeze <https://github.com/donnut>
+// Definitions by: Erwin Poeze <https://github.com/donnut>, Matt DeKrey <https://github.com/mdekrey>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 declare var R: R.Static;
@@ -1402,8 +1402,8 @@ declare namespace R {
         /**
          * Sorts the list according to a key generated by the supplied function.
          */
-        sortBy<T>(fn: (a: any) => string, list: T[]): T[];
-        sortBy(fn: (a: any) => string): <T>(list: T[]) => T[];
+        sortBy<T>(fn: (a: any) => Ord, list: T[]): T[];
+        sortBy(fn: (a: any) => Ord): <T>(list: T[]) => T[];
 
         /**
          * Splits a string into an array of strings based on the given

types/ramda/ramda-tests.ts

@@ -1617,6 +1617,24 @@ matchPhrases(['foo', 'bar', 'baz']);
     R.path(testPath)(testObj); //=> 2
 }
 
+() => {
+    var sortByAgeDescending = R.sortBy(R.compose(R.negate, R.prop('age')));
+    var alice = {
+      name: 'ALICE',
+      age: 101
+    };
+    var bob = {
+      name: 'Bob',
+      age: -10
+    };
+    var clara = {
+      name: 'clara',
+      age: 314.159
+    };
+    var people = [clara, bob, alice];
+    sortByAgeDescending(people); //=> [alice, bob, clara]
+}
+
 () => {
     var sortByNameCaseInsensitive = R.sortBy(R.compose(R.toLower, R.prop('name')));
     var alice = {