Minor grammar fixes, some rewording for clarity.

I think to be grammatically correct, it would have to read:

"A common solution is `a` dependency injection container."

or

 "A common solution is using `a` dependency injection container."

I'm fine with either of those.  

My change was just an attempt to say dependency injection containers were a common solution (probably the best at the moment!), but there are others such as service locators or just just hand-coding all the passed dependencies, as one would in the simple case.

Thanks for writing this book!  It's really helping me grasp Aura.