9.1.5 fixed the old delete mana gem macro, this now requires an addon to work.
Full credits to Dorovon, I just made an addon out of the code he provided.
How to use:
1. Create a macro
#showtooltip
/click DeleteManaGem
/use Conjure Mana Gem
2. Bind macro to something like your old mana gem bind
3. ????????
4. Profit