Adds features and umlaut dummy implementation

.gitignore

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+Gemfile.lock

features/step_definitions/latex.rb

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+When /^I decode the string '([^']*)'$/ do |string|
+  @result = LaTeX.decode(string)
+end
+
+Then /^the result should be '([^']*)'$/ do |value|
+  @result.should == value
+end

features/support/env.rb

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+require 'latex/decode'

features/umlauts.feature

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+Feature: Decode LaTeX umlauts
+	As a hacker who works with LaTeX
+	I want to be able to decode LaTeX umlauts
+
+	Scenario: German umlauts
+		When I decode the string '\"a\"o\"u'
+		Then the result should be 'äöü'

lib/latex/decode.rb

@@ -1,10 +1,13 @@
+# coding: utf-8
 
 require 'latex/decode/version'
 
 module LaTeX
   class << self
     def decode (string)
-      string
+      return string unless string.is_a? String
+
+      string.gsub(/\\"a/, 'ä').gsub(/\\"o/, 'ö').gsub(/\\"u/, 'ü')
     end
   end
 end