Style iOS blue links

Attempts to style default blue links for phone #’s in iOS. Seems to
work in Mail 7.1, spotty support in other clients like Gmail and
Mailbox.

Litmus [lists other
methods](https://litmus.com/blog/update-banning-blue-links-on-ios-device
s) to style or disable blue links in iOS devices, I believe *styling*
links is better practice then *disabling* them for aesthetic reasons.