Added trailing_text handling to abox.py
Added trailing_text handling to abox.py

jefrench/latex2edx,mitocw/latex2edx,jefrench/latex2edx,evheubel/latex2edx,mitocw/latex2edx,jefrench/latex2edx,evheubel/latex2edx,evheubel/latex2edx,mitocw/latex2edx