Detection of opera mobile browser

Phone used those kind of User Agent: 
```
Opera/9.80 (Android 2.3.7; Linux; Opera Mobi/46154) Presto/2.11.355 Version/12.10
```
and tablets are like : 
```
Opera/9.80 (Android 2.3.7; Linux; Opera Tablet/46154) Presto/2.11.355 Version/12.10
```
Merge pull request #83 from jdeniau/master

Detection of opera mobile browser