Clarify introductory sentences (#31)

I found the previous wording a little hard to parse, so I've refactored it.

README.md

@@ -1,6 +1,8 @@
 # imports loader for webpack
 
-Can be used to inject variables into the scope of a module. This is especially useful if third-party modules are relying on global variables like `$` or `this` being the `window` object.
+The imports loader allows you to use modules that depend on specific global variables.
+
+This is useful for third-party modules that rely on global variables like `$` or `this` being the `window` object. The imports loader can add the necessary `require('whatever')` calls, so those modules work with webpack.
 
 ## Installation