Fix documentation and math rendering.
Fix documentation and math rendering.

lpsinger/astropy,mhvk/astropy,astropy/astropy,pllim/astropy,mhvk/astropy,lpsinger/astropy,larrybradley/astropy,larrybradley/astropy,mhvk/astropy,pllim/astropy,astropy/astropy,mhvk/astropy,lpsinger/astropy,larrybradley/astropy,astropy/astropy,lpsinger/astropy,mhvk/astropy,astropy/astropy,lpsinger/astropy,larrybradley/astropy,pllim/astropy,astropy/astropy,pllim/astropy,pllim/astropy,larrybradley/astropy