Switch read_file to ruby

Because `python` is not available out of the box on Ubuntu. They
switched it to `python3`. On CentOS 8 that package is available, but not
installed out of box. So ruby is most reliable now for this use case.

Author: reidmv

tasks/read_file.json

@@ -6,5 +6,8 @@
       "description": "Path to the file to read"
     }
   },
-  "input_method": "environment"
+  "input_method": "stdin",
+  "implementations": [
+    {"name": "read_file.rb"}
+  ]
 }

tasks/read_file.rb

@@ -0,0 +1,9 @@
+#!/opt/puppetlabs/puppet/bin/ruby
+
+require 'json'
+
+params  = JSON.parse(STDIN.read)
+content = File.read(params['path'])
+result  = { 'content' => content }.to_json
+
+puts result