Fix interface default value to be a list instead of a string
Add ping plugin support

The ping plugin is used to measure latency between hosts. Add formula support
for the plugin and example pillar config.
Add write_graphite plugin

The write_graphite plugin allows collectd to write directly to a graphite
server. See pillar.example for configuration.
Merge pull request #5 from iggy/for-upstream-ping-plugin

Add ping plugin support
Merge pull request #6 from iggy/for-upstream-fix-interface-default

Fix interface default value to be a list instead of a string
Merge pull request #7 from iggy/for-upstream-write-graphite-plugin

Add write_graphite plugin
Fix df plugin if all of Device, MountPoint, and FSType aren't set

The df plugin can work with just one of Device, MountPoint, and FSType set.
It will not however function with "None" in any of those fields, so just fix
it to output an empty string if there is no pillar value set.
Merge pull request #8 from iggy/for-upstream-fix-df-plugin

Fix df plugin if all of Device, MountPoint, and FSType aren't set
Fix includes so states can be run independently

If you try to run collectd.df (or any other state) individually, it fails
because it includes the service state file, but the service requires the
package state. We can't just include the package state in the service state
because it would cause a circular dependency.
Merge pull request #9 from iggy/for-upstream-fix-includes

Fix includes so states can be run independently