Update vagrant-rackspace.gemspec

Two digits, at recommended at https://github.com/fog/fog#versioning
Add support for the 'key_name' option, if the user has already uploaded a keypair to rackspace
Update the readme
Add ssh_run support, for vagrant ssh -c
Fix Vagrant 1.4 compatibility and support multiple SSH keys

Vagrant 1.4.0 added support for multiple SSH keys
(mitchellh/vagrant#907)
and changed `private_key_path` to an Array.

This commit ensures we always handle it as array to keep compatible with
both old and new Vagrant versions. Also pass all of the specified keys
to rsync/ssh command.
Appraisal setup (for testing multiple Vagrant versions)
Use appraisal command, rather than having travis run multiple gemfiles
Setup travis to test each Gemfile.
README note about tty support

@krames - updated the documentation as requested, but #58 needs to be fixed so upgrading doesn't introduce new limitations.
Update README.md
Merge pull request #58 from avelis/master

Fix Vagrant 1.4 compatibility and support multiple SSH keys
Merge pull request #62 from maxlinc/patch-2

README note about tty support
Merge pull request #53 from cyli/keypairs_support

Add uploaded keypair support
Merge pull request #49 from maxlinc/patch-1

Update vagrant-rackspace.gemspec
fix broken feature tests
remove networks warning as vagrant-rackspace now supports networks
Merge pull request #63 from rackspace/fix_tests

fix broken feature tests
Merge pull request #64 from rackspace/remove_net_warning

remove networks warning as vagrant-rackspace now supports networks
Merge pull request #57 from domcleal/ssh_run

Add ssh_run support, for vagrant ssh -c
Merge pull request #60 from maxlinc/appraisals

Appraisals