Fixes #14 Update node attributes to strings and use use_inline_resources if it is available

Fix for #14 

Changed attribute references to strings and added a conditional use_inline_resources which appeased foodcritic.
There's one validation (do I know about this filename or not), which arguably actually is more of a hindrance than a benefit (and wholly unnecessary here, where we know the name of the conf file). The rest is syntactic sugar I wrote in a fit of not wanting to write the same parameters to a template resource over and over and over again. Given #15 splunk_template is going to need modification at least, scrapping at worst.