Require reader option in CLI. Closes #35.

bin/mdtranslator

@@ -28,7 +28,7 @@ with options to select the input file reader, select writer output format, show
 in XML outputs, and choose level of validation for JSON inputs.
 	LONGDESC
 	# define cli options
-	method_option :reader, :aliases => '-r', :desc => 'Reader to read your input metadata file', :enum => %w{mdJson}
+	method_option :reader, :aliases => '-r', :desc => 'Reader to read your input metadata file', :enum => %w{mdJson}, :required => true
 	method_option :writer, :aliases => '-w', :desc => 'Writer to create your output metadata file, leave blank to validate input only', :enum => %w{iso19115_2 iso19110 html}
 	method_option :validate, :aliases => '-v', :desc => 'Specify level of validation to be performed', :enum => %w{none normal strict}, :default => 'normal'
 	method_option :showAllTags, :aliases => '-s', :desc => 'Include tags for unused attributes', :type => :boolean, :default => false