Fix #57: Map is broken if event has no coords
Fix #57: Map is broken if event has no coords

Drawing an event on the map only works if coords are supplied. This
commit filters events that do not have coordinates set yet.

kimdhendrick/coderetreat.github.io,coderetreat/coderetreat.github.io,tpd-opitz/coderetreat.github.io,yugangbai/coderetreat.github.io,coderetreat/coderetreat.github.io,yugangbai/coderetreat.github.io,yugangbai/coderetreat.github.io,kimdhendrick/coderetreat.github.io,tpd-opitz/coderetreat.github.io,svenlange/coderetreat.github.io,coderetreat/coderetreat.github.io,SeattleSoftwareCraftsmanship/coderetreat.github.io,SeattleSoftwareCraftsmanship/coderetreat.github.io,svenlange/coderetreat.github.io,kimdhendrick/coderetreat.github.io,tpd-opitz/coderetreat.github.io,yugangbai/coderetreat.github.io,svenlange/coderetreat.github.io,svenlange/coderetreat.github.io,coderetreat/coderetreat.github.io,SeattleSoftwareCraftsmanship/coderetreat.github.io