New option to force placeholders

This release includes the new 'matchCols' option, which will force the addition of the maximum number of placeholders for the given number of columns, regardless of how many items already exists. Useful for responsive layouts where the column count may change.

Option updates

Added data attribute for setting columns, plus other minor additions

Added options

Added options to specify children and placeholder element types.

Initial release

v1.0.0

Initial commit