Change PNG badges in README to SVGs

SVG versions look better in any display.
Merge pull request #612 from tute/patch-1

Change PNG badges in README to SVGs
Minor typo fix "search engine" -> "search engines"

Thanks for a great gem - HTH, Eliot
Minor typo fix "character" -> "characters"
Merge pull request #621 from eliotsykes/patch-2

Minor typo fix "character" -> "characters"
Merge pull request #620 from eliotsykes/patch-1

Minor typo fix "search engine" -> "search engines"
Fixed gem bundling when using rbx-2 on Travis CI
Fix spelling of 'sufficient' in initializer.rb
FASTER BETTER STRONGER
Merge pull request #623 from derwiki/HEAD

Fix spelling of 'sufficient' in initializer.rb
Merge pull request #624 from joshk/patch-1

FASTER BETTER STRONGER