See IRS Publication 970 at
https://www.irs.gov/pub/irs-pdf/p970.pdf Section 6 starting at the bottom of page 38.
The president recently signed this deduction back into law, and basically caught the IRS with their pants down. So until the IRS approves the 2017 forms (the *ELECTRONIC* versions of the forms) required for this, TTX can not include it in their software.
I don't see this happening very fast either, as it's not just a simple matter of issuing an updated form. The IRS has to change their computer systems to deal with the change now, and they have to do it during "ACTIVE" filing. So I'm not expecting it to happen until after the Apr 16th tax filing deadline myself.
Meanwhile, go ahead and file your return "as is". Then when the IRS "gets around to" updating things on their end, you can file an amended return to claim the expenses.