Fix nice parameter to accept -20

Without this commit the range for nice is -19 to 19 which is incorrect.
nice(1) states that the valid values range from -20 to 19.

README.md

@@ -70,7 +70,7 @@ page.
  * `instances`    - optional - defaults to "UNLIMITED"
  * `wait`         - optional - based on $protocol will default to "yes" for udp and "no" for tcp
  * `service_type` - optional - type setting in xinetd
- * `nice`         - optional - integer between -19 and 19
+ * `nice`         - optional - integer between -20 and 19, inclusive.
 
 ### Sample Usage
 

manifests/service.pp

@@ -38,7 +38,7 @@
 #   $access_times   - optional
 #   $log_type       - optional
 #   $bind           - optional
-#   $nice           - optional
+#   $nice           - optional - integer between -20 and 19, inclusive.
 #
 # Actions:
 #   setups up a xinetd service by creating a file in /etc/xinetd.d/
@@ -112,7 +112,7 @@
   if $nice != undef {
     validate_integer($nice)
 
-    if $nice < -19 or $nice > 19 {
+    if $nice < -20 or $nice > 19 {
       fail("Invalid value for nice, ${nice}")
     }
   }

spec/defines/xinetd_service_spec.rb

@@ -87,7 +87,7 @@
   end
 
   # nice values, good
-  [-19,9,19].each do |i|
+  [-20,0,9,19].each do |i|
     describe "with nice #{i}" do
       let :params do
         default_params.merge({ :nice => i })
@@ -98,7 +98,7 @@
   end
 
   # nice values, bad
-  ['-20','90','foo',-20,90].each do |i|
+  ['-21','90','foo',-21,90,20].each do |i|
     describe "with nice #{i}" do
       let :params do
         default_params.merge({ :nice => i })