Can install RadRails on Eclipse Luna 4.4.2

I am trying to install the RadRails plug-in on a fresh Eclipse Luna instance (4.4.2), using the following update site: http://ift.tt/KNKjIh

But it always fails with the error below:

Cannot complete the install because one or more required items could not be found. Software being installed: Aptana RadRails 2.0.5.1278709071-79-7D7BFZcLCUQRF2NWAQhRBC1qP (com.aptana.radrails.feature.feature.group 2.0.5.1278709071-79-7D7BFZcLCUQRF2NWAQhRBC1qP) Missing requirement: Aptana Editor Infrastructure 2.0.5.1278523018-8o57z9icbz-hWlJZG (com.aptana.ide.feature.editors.feature.group 2.0.5.1278523018-8o57z9icbz-hWlJZG) requires 'org.eclipse.update.ui 0.0.0' but it could not be found

Cannot satisfy dependency: From: Aptana Web Development Tools 2.0.5.1278614541-7D-7O7iRJci-jVhz-KFyoijH (com.aptana.ide.feature.feature.group 2.0.5.1278614541-7D-7O7iRJci-jVhz-KFyoijH) To: com.aptana.ide.feature.editors.feature.group [2.0.5.1278523018-8o57z9icbz-hWlJZG] Cannot satisfy dependency: From: Aptana RadRails 2.0.5.1278709071-79-7D7BFZcLCUQRF2NWAQhRBC1qP (com.aptana.radrails.feature.feature.group 2.0.5.1278709071-79-7D7BFZcLCUQRF2NWAQhRBC1qP) To: com.aptana.ide.feature.feature.group [2.0.5.1278614541-7D-7O7iRJci-jVhz-KFyoijH]

What should I do to install RadRails?