Use SVG for status badges in README

http://shields.io/ provides many standardized badges for OSS. The PNG versions provided by Shields are similar to the images currently used, but the SVG versions added here are more legible on high pixel density displays.

Inch Pages themselves provide a SVG badge, so use it!
Merge pull request #1157 from seanlinsley/patch-1

Use SVG for status badges in README
Move Readline-loading specs inside normal suite

This simplifies our Rake and Travis config.
Merge pull request #1156 from pry/readline-specs

Move Readline-loading specs inside normal suite
use HEREDOC's to improve readability of eval string.
add 'default' to the list of reserved keys & improve err msg.