Styling up Jump Nav text box

Summary:
This actually gives it a smooth look across all OS and browsers. Copy-paste from form inputs.

= Motivation (aka Disclaimer) =

I felt kind of... disturbed that it looked different in every browser / OS combination I have at my disposal. The range is from ugly (Chrome on Ubuntu) to pretty (IE9 on Win7 ¬.¬). I give a few examples

 - Ubuntu
   - Firefox
     - Actually looking very nice. Rounded borders and orange border on focus are default from UA style sheet?
   - Chrome
     - Looks ugly. 2px inset mid-grey border. What you would expect from Win '95
     - 1px inset mid-grey border (Win '98 style) + orange webkit outline.
 - Windows
   - IE9
     - Nice blocky text input with black border. Blue border upon hover. Really black border on focus?
   - IE10
     - Kind of same as IE9, though I had the feeling that it had a deeper black border
   - Firefox
     - Looks so normal that it is actually boring
   - Chrome
     - Looks pretty much normal, until focus where you get the webkit outlines. Ugly

No Mac, since I have no Mac. Also no iPhone/iPad. Have Android 4.1/WP8, though I never visited Phabricator with them

Test Plan:
Looked at it in

 - Ubuntu
   - Mozilla Firefox
   - Google Chrome
 - Windows 7/8
   - IE 9/10
   - Opera (Opera?)
   - Mozilla Firefox
   - Google Chrome

Everything smooth (exceptions in case of no border-radius/box-shadow)

Reviewers: epriestley, btrahan, chad

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5515