Add Nexus support (Nexus 5, Nexus 7 & Nexus 10)

[EsKuel]

Hi !

Nexus 10 and 7 are missing in patterns file so the gem currently recognise them as handheld device.
I also add Nexus 5 in pattern file to add the whole family :)

[carsonb]

Hi there! Thanks so much for the PR.

I think browser sniffer is being far too picky about what's a handheld and what's a tablet. Android docs from the distant past talk about it being the presence of "Mobile" defining handhelds, and the lack of it defining tablets: http://android-developers.blogspot.ca/2010/12/android-browser-user-agent-issues.html