docs($rootScope): fix typos and minor wording tweaks on $watch

Author: mernen

src/ng/rootScope.js

@@ -221,18 +221,18 @@ function $RootScopeProvider(){
        *   reruns when it detects changes the `watchExpression` can execute multiple times per
        *   {@link ng.$rootScope.Scope#$digest $digest()} and should be idempotent.)
        * - The `listener` is called only when the value from the current `watchExpression` and the
-       *   previous call to `watchExpression` are not equal (with the exception of the initial run
+       *   previous call to `watchExpression` are not equal (with the exception of the initial run,
        *   see below). The inequality is determined according to
-       *   {@link angular.equals} function. To save the value of the object for later comparison
+       *   {@link angular.equals} function. To save the value of the object for later comparison, the
        *   {@link angular.copy} function is used. It also means that watching complex options will
        *   have adverse memory and performance implications.
        * - The watch `listener` may change the model, which may trigger other `listener`s to fire. This
        *   is achieved by rerunning the watchers until no changes are detected. The rerun iteration
-       *   limit is 100 to prevent infinity loop deadlock.
+       *   limit is 100 to prevent an infinite loop deadlock.
        *
        *
        * If you want to be notified whenever {@link ng.$rootScope.Scope#$digest $digest} is called,
-       * you can register an `watchExpression` function with no `listener`. (Since `watchExpression`,
+       * you can register a `watchExpression` function with no `listener`. (Since `watchExpression`
        * can execute multiple times per {@link ng.$rootScope.Scope#$digest $digest} cycle when a change is
        * detected, be prepared for multiple calls to your listener.)
        *