add information about dependency on NUnit version 2.6.3

Author: ShaKaRee

doc/Concordion/Integration/ReSharper.html

@@ -15,12 +15,13 @@ <h3>ReSharper</h3>
               Concordion.NET</a>.</li>
 	  <li>Install ReSharper</li>
 	  <li>Copy Concordion.NUnit.dll into the addin directory of your ReSharper 
-	  installation (&lt;resharper-installation-path&gt;\Bin\addins\)<ol>
-		  <li>Notice: If you aren't using the build-in NUnit version, but your 
+	  installation (&lt;resharper-installation-path&gt;\Bin\addins\)<ul>
+		  <li>Using specific NUnit installation: If you aren't using the build-in NUnit, but your 
 		  specified NUnit installation (ReSharper -&gt; Options ... -&gt; Tools -&gt; 
 		  Unit Testing -&gt; NUnit), you have to copy Concordion.NUnit.dll into the 
 		  used NUnit installation (&lt;nunit-installation-path&gt;\bin\addins\).</li>
-	  </ol>
+		  <li>Make sure that NUnit version 2.6.3 is used in any situation.</li>
+	  </ul>
 	  </li>
 	  <li>Run your Concordion.NET acceptance tests with ReSharper<ol>
 		  <li>To run a single test directly from the editor: Click on the 

doc/Download.html

@@ -60,6 +60,8 @@ <h1>Release Notes</h1>
 		<a href="https://github.com/concordion/concordion-net/commits/master">Version
             History on GitHub</a></p>
         <h2>Concordion.NET 1.2.0 - March 2015</h2>
+		  <p>This release of Concordion.NET needs NUnit version 2.6.3 to run the 
+		  executable specifications.</p>
 		  <h3>Features</h3>
 		  <ul>
 			  <li>Enable <a href="RunningTests.html#resharper">running 

doc/RunningTests.html

@@ -31,7 +31,8 @@
         <h1>Run Concordion.NET Acceptance Tests with NUnit</h1>
         <p>Concordion.NET integrates with one of the
           most popular automated testing frameworks. Concordion.NET provides an NUnit Addin 
-		that allows running <a href="index.html">accetpance tests</a> with any NUnit environment that supports NUnit Addins. 
+		that allows running <a href="index.html">accetpance tests</a> with any NUnit environment that supports NUnit Addins 
+		(NUnit version 2.6.3). 
 		We describe how to run Concordion.NET tests with </p>
 		  <ul>
 			  <li><a href="#stand-alone">stand alone</a> NUnit test 
@@ -87,7 +88,7 @@ <h3>Run Concordion.NET tests with the NUnit GUI runner</h3>
         <ol>
           <li><a href="Download.html">Download
               Concordion.NET</a>.</li>
-          <li>Download and <a class="externalLink" href="http://www.nunit.org/index.php?p=installation&amp;r=2.6.3">install NUnit</a>.</li>
+          <li>Download and <a class="externalLink" href="http://www.nunit.org/index.php?p=installation&amp;r=2.6.3">install NUnit version 2.6.3</a>.</li>
 			<li>Coppy the Concordion.NUnit.dll into the addin directory of 
 		  your NUnit installation
             (&lt;NUnit-installation-path&gt;\bin\addins). <br>Please, make sure to use the latest version of this DLL, when
@@ -117,7 +118,7 @@ <h3>Run Concordion.NET tests with the console runner</h3>
         <ol>
           <li><a href="Download.html">Download
               Concordion.NET</a>.</li>
-			<li>Download and <a class="externalLink" href="http://www.nunit.org/index.php?p=installation&amp;r=2.6.3">install NUnit</a>.</li>
+			<li>Download and <a class="externalLink" href="http://www.nunit.org/index.php?p=installation&amp;r=2.6.3">install NUnit version 2.6.3</a>.</li>
             <li>Copy the Concordion.NUnit.dll into the addin directory of 
 		  your NUnit installation
             (&lt;NUnit-installation-path&gt;\bin\addins). <br>Please, make sure to use the latest version of this DLL, when