Add tests, request scope, HttpRequest bindings and remove custom inject decorator

[jstasiak]

Hey,

First of all – thank you for the useful project. I went ahead and make some changes to make it more suitable for my needs, I decided to send you all of them in a single pull request but I'm happy to split them into four pull requests (it's one commit per pull request).

The changes are as follows:

• automated test suite – I needed to make sure I wasn't breaking things when making changes
• middleware instead of custom inject decorator – this is in order to always use the same inject decorator to avoid confusion and reduce potential breakage when something in Injector changes
• custom request scope – this will be useful to cache/share type instances during handling of a single request but not leak them to other requests
• binding HttpRequest so that current request can be injected

[asyncee]

Hello, @jstasiak! I have reviewed your changes and want to say that it is very nice work. Thanks! I had to fork your branch to use in my pet project until this PR gets merged by @blubber (i hope).

Also i want to thank @blubber for such a nice integration library.

[blubber]

I have been out of the country on vacation. I’ll take a look at this as soon as I get back next week. Thanks)

[blubber]

Great contributions, thanks! I'm going to merge it right now and setup the integration with Travis later.

[jstasiak]

Cheers!