bug-58 Card UI:

1. Include genzeb's filp library to create 3D filp view.
2. Include Picasso library for download and caching images.
3. Link to Wikipeddia.
3. Use icomoon font on previous and next button.
4. When it can't display card content correctly, show error card UI. 

I found a trick here. You switch the langCode when user flips the card. So, the target data is downloaded from server. But only the shown card's language is downloaded. That may produce a minor issue when user flip back to another language, disconnect their internet and press previous word. He/she may see an error dialog and continue to see the already downloaded card.

We should download both selectedLanguage and nativeTongue at the same time in the future. Let's file this as a follow-up bug.