Updates Apache HTTP Client to current 4.5.1

This does create some warnings because several methods and classes
are deprecated in the meantime.

Author: EBichel

pom.xml

@@ -59,7 +59,7 @@
         <commons.lang.version>2.6</commons.lang.version>
         <guava.version>14.0.1</guava.version>
         <hamcrest.version>1.3</hamcrest.version>
-        <httpclient.version>4.2.5</httpclient.version>
+        <httpclient.version>4.5.1</httpclient.version>
         <jackson.version>2.2.0</jackson.version>
         <jetty.version>9.1.1.v20140108</jetty.version>
         <joda.time.version>2.2</joda.time.version>