Revert "Upgrade underscore.string.min.js."

This reverts commit e5c7fdda03.

Unfortunately this change broke bundling on sandboxes, so reverting
it so that master isn't left in a bad state.

common/static/js/vendor/underscore.string.min.js

@@ -1 +0,0 @@
-../../../../node_modules/underscore.string/dist/underscore.string.min.js

lms/static/lms/js/require-config.js

@@ -18,11 +18,12 @@
             }
         };
         defineDependency("jQuery", "jquery");
-        defineDependency("s", "underscore.string");
-        // Underscore.string no longer installs itself directly on "_". For compatibility with existing
-        // code, add it to "_" with its previous name.
-        if (window._ && window.s) {
-            window._.str = window.s;
+        defineDependency("_", "underscore");
+        if (window._ && window._.str) {
+            define("underscore.string", [], function () {return window._.str;});
+        }
+        else {
+            console.error("Expected _.str (underscore.string) to be on the window object, but not found.");
         }
         defineDependency("gettext", "gettext");
         defineDependency("Logger", "logger");

package.json

@@ -6,8 +6,7 @@
     "edx-pattern-library": "0.10.4",
     "requirejs": "~2.1.22",
     "uglify-js": "2.4.24",
-    "underscore": "~1.8.3",
-    "underscore.string": "~3.3.4"
+    "underscore": "~1.8.3"
   },
   "devDependencies": {
     "jshint": "^2.7.0",