refresh travis setup

- indicate that we're keen on caching
- lets not install non-essential gems
- test against a larger variety of ruby interpreters however, lets allow some failures
- enable speedy greens (http://blog.travis-ci.com/2013-11-27-fast-finishing-builds)
README, LICENSE and .gitignore refresh

- ignore bin directories for those that `bundle install --binstubs`
- ensure Markdown files are rendered that way on Github
- refresh README.md with svg badges and ensuring Supported Ruby Versions are front and centre
refresh Rakefile

- replace Gem::PackageTask with Bundler::GemHelper in
- add description to Rspec Rake task as well as add a common alias for test to simply run spec
refresh .gemspec

- ensure .gemspec is using latest Gem::Specification behaviour
- make sure that test gems are not a 'add_development_dependency'
use new Rake tasks
refresh spec_helper

- move FakeWeb out into a support file
- enforce Rspec 3 syntax
use Rspec 3.0 expect syntax
use latest stable Rspec
use gem name specifically
ensure badges are above the fold for more glance-ability
more confident ruby version support
document development installation instructions too
include more installation options
err on the safer side and use bundle exec instead of assuming --binstub'd installed gems
temporarily ensure test dependencies are installed #88 should fix this
Merge pull request #87 from karlfreeman/readme-license-gitignore-refresh

README, LICENSE and .gitignore refresh
Alias #to_xml to #text
constrain to 1.8.7 compatible version of Rake

- http://docs.seattlerb.org/rake/History_rdoc.html#label-10.1.2+/+2014-03-24
constrain to 1.8.7 compatible version of Rake

- http://docs.seattlerb.org/rake/History_rdoc.html#label-10.1.2+/+2014-03-24
Use lower camel case for TwiML verb arguments

The existing example will not camel case the existing finish_on_key argument to return finishOnKey as expected.