reworked filtering rvm tasks
use fallback values for rvm variables
add :on_no_matching_servers => :continue to bundler:bundle_config so it does not fail when no servers matched
Merge pull request #43 from engineyard/bugfix/filtering_rvm_run_issue_43

eycap v0.6.8 fails to detect rvm gem path with rvm-capistrano v1.4.3