abstracted data structure to make easier to add more languages
[js/cartas.js]
switched to sourceLanguage and targetLanguage vars instead of direct
references to english and spanish
[js/spanishVocab.js]
simplified data format
switched to using keys to denote language of vocab items
additional refactors to abstract functionality

[index.html]
- updated card display value to use the displayLanguage field of the
currentWord object
[js/cartas.js]
- extracted inline function defenitions to prototype for AppViewModel
- AppViewModel now accepts a source and target language as arguments
- displayLanguage is an observable field
- moved card display value to template
Merge branch 'master' of http://github.com/jurgns/flashcartas
[js/spanishVocab.js]
converted the added verbs into the newer data format.

Conflicts:
	js/spanishVocab.js