Add more LaTeX commands
Add AMSSymb
Fix unneeded import in AMSSymb.hs
Comment the constructors StillCovered and AgainCovered in Beamer.hs
Export quad and qquad in AMSMath.hs
Merge pull request #34 from romildo/jrm

New package implemented: AMSSymb. Additions to AMSMath and beamer. Some fixes.