remove matrix tag from travis env yaml

"matrix" doesn't belong in env param according to
http://docs.travis-ci.com/user/build-configuration/#The-Build-Matrix

Although it works as-is, having matrix under env prevents exclusions
from working.
travis test matrix includes rvm 2.0.0 when puppet >= 3.2

Puppet 3.2 and higher are supported on Ruby 2.x according to
http://docs.puppetlabs.com/guides/platforms.html#ruby-versions
so it makes sense to test this module on the same matrix.

Exclude older versions of Puppet from the test matrix
under rvm 2.0.0 because older versions of Puppet definitely
fail on rvm 2.0.0.
travis test matrix excludes rvm 1.9.3 when puppet < 3.0

http://docs.puppetlabs.com/guides/platforms.html#ruby-versions
asserts that Puppet older than 3.0 do not support Ruby 1.9.3

After this commit, the travis test matrix aligns with
the PuppetLabs platform support matrix as currently published.
git ignores .bundle/

.bundle is not in upstream, so presumably
it's not part of any workflow.
Merge pull request #31 from jumanjiman/travis

align travis test matrix with puppetlabs platform support matrix