Improve "connection reset" error handling when mojang is down

[Slind14]

It might worth looking into a more human friendly output in case of this exception (mojang auth down):

java.net.SocketException: Connection reset
    at java.net.SocketInputStream.read(Unknown Source)
    at java.net.SocketInputStream.read(Unknown Source)
    at sun.security.ssl.InputRecord.readFully(Unknown Source)
    at sun.security.ssl.InputRecord.read(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at sun.net.www.protocol.https.HttpsClient.afterConnect(Unknown Source)
    at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(Unknown Source)
    at com.skcraft.launcher.util.HttpRequest.execute(HttpRequest.java:129)
    at com.skcraft.launcher.auth.YggdrasilLoginService.login(YggdrasilLoginService.java:42)
    at com.skcraft.launcher.dialog.LoginDialog$LoginCallable.call(LoginDialog.java:326)
    at com.skcraft.launcher.dialog.LoginDialog$LoginCallable.call(LoginDialog.java:314)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)