Updated appveyor.yml to create build matrix
Updated appveyor.yml to create build matrix

christkv/bson-ext,guymguym/bson-ext,guymguym/bson-ext,christkv/bson-ext,VikramTiwari/bson-ext,msmiley/bson-ext,VikramTiwari/bson-ext,VikramTiwari/bson-ext,guymguym/bson-ext,msmiley/bson-ext,msmiley/bson-ext,christkv/bson-ext,christkv/bson-ext