Fix issue where 'conda index' with old packages would create bad metadata
Fix issue where 'conda index' with old packages would create bad metadata

This issue is also described here:
https://groups.google.com/a/continuum.io/forum/#!topic/conda/UXX9E7LkVMA

dan-blanchard/conda-build,shastings517/conda-build,mwcraig/conda-build,ilastik/conda-build,rmcgibbo/conda-build,shastings517/conda-build,ilastik/conda-build,ilastik/conda-build,frol/conda-build,frol/conda-build,dan-blanchard/conda-build,rmcgibbo/conda-build,rmcgibbo/conda-build,shastings517/conda-build,dan-blanchard/conda-build,sandhujasmine/conda-build,sandhujasmine/conda-build,mwcraig/conda-build,frol/conda-build,mwcraig/conda-build,sandhujasmine/conda-build