create resolv.conf inside postfix chroot (for CentOS support)
spec test for chrooted resolv.conf file creation
Created chroot_files attribute to handle postfix chroot files
README: added Chroot files section
Added more files to chroot_files: etc/localtime, etc/services, etc/resolv.conf, etc/hosts, etc/nsswitch.conf, etc/nss_mdns.config
chroot etc directory creation fixed to take into account the queue_directory attribute
Tests added for all the created chroot_files
Add support for optional cmd in table params
Update README with cmd option information and example
spec: improve test suite and configuration
Merge pull request #8 from onddo/centos-support-2

[CentOS support fix] Create some required files inside chroot

In addition to the merge itself (and a conflict with spec/default_spec.rb), I
have added three additional tests to test the behavior on own defined chroot
files, ensure that :cp (as symbol) is also supported and logs a error on
unknown file chroot modes.
Merge pull request #10 from loxley/postalias-table-support

Add support for optional cmd in table params (e.g. postalias)

And a small README extension