Support for other languages

### Available languages
Chinese (Mandarin): #811
German: #571*
Swedish: #257*

\* Requires Tensorflow 1.x (harder to set up).

### Requested languages (not available yet)
Arabic: #871
Czech: #655
English: #388 (UK accent), #429 (Indian accent)
French: #854 
Hindi: #525
Italian: #697
Polish: #815
Portuguese: #531 
Russian: #707
Spanish: #789
Turkish: #761
Ukrainian: #492