Adopt strict mode throughout the codebase

src/boot/boot0.js

@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  This file starts the process of "booting" Jasmine. It initializes Jasmine,
  makes its globals available, and creates the env. This file should be loaded

src/boot/boot1.js

@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  This file finishes 'booting' Jasmine, performing all of the necessary
  initialization before executing the loaded environment and all of a project's

src/boot/jasmine-core.js

@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  * Note: Only available on Node.
  * @module jasmine-core