Add the option to resolve dependencies by name

[brototyp]

Implements #8

This PR add functionality to resolve dependencies by name or in this case tag.
In order to do so, I changed the following:

A component no longer has a tag: String but an let identifier: AnyHashable. This identifier is used to reference the Component as well as the instance in the Container (ComponentStack and InstanceStack). I also added a ComponentIdentifier struct that uses the Type of the factory as well as an optional tag to calculate the hashValue. So instead of a String of the Type, we now use the hashValue of the type to identify a Component or an instance in our Container.

Next I added an optional tag: AnyHashable parameter to all functions that are used to register or resolve dependencies.

I didn't write any documentation in the README yet since I first wanted to get some feedback about this first. I am looking forward to hear ideas on how this could be improved.

[benjohnde]

Oh my gosh that's amazing! @brototyp I am going to review your PR tomorrow. Thank you so much for your work! I am so happy right now to see some interest in that tiny DI library :)

[benjohnde]

LGTM, I like the usage of AnyHashable and also the new ComponentIdentifier. Thank you very much for your contribution!

[brototyp]

Wohoo. Awesome! Thanks for your fast review!

[benjohnde]

Ah damn, I merged it a bit too fast, as you mentioned the missing documentation in the README.md. Well @brototyp, feel free to open another PR. I am going to give #22 another shot. After that I will bump the version to 1.6.0 and release your contribution!

[brototyp]

Ah damn, I merged it a bit too fast, as you mentioned the missing documentation in the README.md. Well @brototyp, feel free to open another PR. I am going to give #22 another shot. After that I will bump the version to 1.6.0 and release your contribution!

Oh yeah. I totally forgot as well. Looks like we both were a little to excited about it 😊
I'll try to write a first draft of the README and will create a PR in that regard.

[brototyp]

Hey @benjohnde, just a gentle ping from my side. Is there any way we can get the release train rollin'? Either straight as it is, or with #22? (Also: Do you need any support on #22? Maybe some brainstorming and bouncing off ideas?)

[benjohnde]

I am ultimately sorry for having merged your contribution and not releasing it. I totally love the way you implemented the resolving dependencies by name feature. I am going to finalise the release tomorrow @brototyp 🎉🚀.

[brototyp]

Don't worry about it. I know that it's hard to follow up on such side projects.

[benjohnde]

I just finished the release, you are free to use the new version 1.6.0. Podspec was also pushed to Cocoapods 🎉 !