Upgraded project version to 4.1-alpha1-SNAPSHOT

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1586750 13f79535-47bb-0310-9956-ffa450edef68
Upgraded JRE level to 1.6; upgraded Commons IO to version 2.4; upgraded JUnit to version 4.11

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1586756 13f79535-47bb-0310-9956-ffa450edef68
Use Locale#ROOT instead of Locale#ENGLISH or Locale#US for lower / upper case conversions

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1586757 13f79535-47bb-0310-9956-ffa450edef68