document how to disable streaming in rails, see #555

streaming only improves the perceived performance
fix readme
slimrb: Remove deprecated plugin options -l and -t
remove StaticTiltEngine, refactoring
minor cleanup
add minimum required ruby version
Use the new build env on Travis

faster vms, more ram, more cpu, better boot times

removed bundler update as latest bundler is installed
minor cleanup
Merge pull request #564 from joshk/patch-1

Use the new build env on Travis
don't escape in template
use StaticFreezer + StaticMerger for optimization

see https://github.com/judofyr/temple/issues/82