I think the current version of GRUB2 does not have support for loading and decrypting LUKS partitions by itself (it contains some ciphers but I think they are used only for its password support). I cannot check the experimental development branch, but there are some hints in the GRUB page that some work is planned to implement what you want to do.
However, if you are trying to encrypt the whole disk for security reasons, plese note that an unencrypted boot loader (like TrueCrypt, BitLocker or a modified GRUB) offers no more protection than an unencrypted /boot partition (as noted by JV in a comment above). Anybody with physical access to the computer can just as easily replace it with a custom version. That is even mentioned in the article at xercestech.com you linked:
To be clear, this does not in any way make your system less vulnerable to offline attack, if an attacker were to replace your bootloader with their own, or redirect the boot process to boot their own code, your system can still be compromised.
Note that all software-based products for full disk encryption has this weakness, no matter if they use an unencrypted boot loader or an unencrypted boot/preboot partition. Even products with support for TPM (Trusted Platform Module) chips, like BitLocker, can be rooted without modifying the hardware.
A better approach would be to:
- decrypt at the BIOS level (in motherboard or disk adapter or external hardware [smartcard], with or without a TPM chip), or
- carry the PBA (preboot authorization) code (the /boot partition in this case) in a removable device (like a smartcard or an USB stick).
To do it the second way, you can check the Linux Full Disk Encryption (LFDE) project at: http://lfde.org/ which provides a post-install script to move the /boot partition to an USB memory, encrypting the key with GPG and storing it in the USB too. In that way the weaker part of the boot pathway (the non-encrypted /boot partition) is always with you (you will be the only one with physical access to the decrypting code AND the key).