German Localization

[roschlau]

I wanted to make a localized German version of the app for myself, and decided to push the changes I made back upstream, in case you're interested :)

🔧 Changes

• Use string resources instead of Enum names for the temperature difference adjective
• Add strings.xml for German (de) locale.

📝 Notes

I've added a test that runs with the de qualifier and checks the summary for the German equivalent of "It's the same this afternoon as yesterday afternoon."
This test should succeed when ran in PST, but right now, the test fails for me, because I'm in a timezone where the 1484180189 timestamp is actually during the night, so the summary changes accordingly - which is correct behavior, but the tests are not setup to deal with timezone differences. This is actually making a few other tests fail as well.
@mandybess I feel like fixing this should be a separate issue, and not part of this PR, right?

[roschlau]

I should also mention, this PR probably only makes sense once #11 is completed. If that issue brings anything new that might need adjustment in this PR (like another string that needs to be localized) I'll happily take care of that.

[mandybess]

Hi @Hikaru755 ! Thank you so much for this! I finally resolved #11 (see #15) if you wouldn't mind updating this, I'd be happy to merge!

[roschlau]

@mandybess Great, I just made my adjustments to make it work with the changes and pushed them into the PR! Awesome work with the app btw, I'm so happy to now have my beloved metric units as well :)

[roschlau]

@mandybess Oh and seeing that Tropos is now also available outside the US through the Play Store - if you want to have the Play Store listing match the app by giving it a proper German translation hit me up, I'd be happy to work with you on that!