misc (v0.1.0)

- add method versionStr()
- add constructor parameter maxPhoneWidth
- integrate rules from detectmobilebrowsers.com as fallback
- fuzzy phone/tablet differentiation based on screen.width
- add method isPhoneSized()
- copy mobileGrade logic from Mobile-Detect (php)
- extend tests
- bugfix issue#1
- extend Readme#Alternatives