Update to use class method

exercises/practice/isogram/.meta/example.coffee

@@ -1,5 +1,5 @@
 class Isogram
-  isIsogram: (phrase) ->
+  @isIsogram: (phrase) ->
     seen = {}
     for char in phrase.toLowerCase()
         cp = char.charCodeAt(0)

exercises/practice/isogram/isogram.coffee

@@ -1,4 +1,4 @@
 class Isogram
-  isIsogram: (phrase) ->
+  @isIsogram: (phrase) ->
 
 module.exports = Isogram

exercises/practice/isogram/isogram.spec.coffee

@@ -1,73 +1,72 @@
 Isogram = require './isogram'
 
 describe 'Isogram', ->
-  iso = new Isogram()
   it 'empty string', ->
     phrase = ''
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual true
 
   xit 'isogram with only lower case characters', ->
     phrase = 'isogram'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual true
 
   xit 'word with one duplicated character', ->
     phrase = 'eleven'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'word with one duplicated character from the end of the alphabet', ->
     phrase = 'zzyzx'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'longest reported english isogram', ->
     phrase = 'subdermatoglyphic'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual true
 
   xit 'word with duplicated character in mixed case', ->
     phrase = 'Alphabet'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'word with duplicated character in mixed case, lowercase first', ->
     phrase = 'alphAbet'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'hypothetical isogrammic word with hyphen', ->
     phrase = 'thumbscrew-japingly'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual true
 
   xit 'hypothetical word with duplicated character following hyphen', ->
     phrase = 'thumbscrew-jappingly'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'isogram with duplicated hyphen', ->
     phrase = 'six-year-old'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual true
 
   xit 'made-up name that is an isogram', ->
     phrase = 'Emily Jung Schwartzkopf'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual true
 
   xit 'duplicated character in the middle', ->
     phrase = 'accentor'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'same first and last characters', ->
     phrase = 'angola'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false
 
   xit 'word with duplicated character and with two hyphens', ->
     phrase = 'up-to-date'
-    result = iso.isIsogram(phrase)
+    result = Isogram.isIsogram(phrase)
     expect(result).toEqual false