[issues-5] Adds flags for types of support

Using an nth-* approach along side data-attribute approach. Each
support is independant of each other.
[issues-5] Adds new private function for column selectors

In order to keep styles to a minimum the css selectors need to be
built using string concatination. This function builds the
css styles needed for each approach and allows for multiple approaches
to be used at once or alone.
[issues-5] Adds helper function for nth-child-hack

In order to support IE8 the adjacent selector is abused to handle
psudo support for nth-child on IE8. It is not full support since
there is a limit to the number of items that can be supported.
However it does give the dynamic nature for the elements that fall
within the limit. For best IE8 support the data-attribute should
be used.
[issues-5] Adds mixin to generate styles for each column block
[issues-5] Replaces original data-column selector with _column

The new _column mixin builds the correct selector(s) needed for
each column and applies the styles given.
[issues-5] Adds new mixin for setting processing options

The options effect the types of styes column-policy generates.
[issues-5] Adds .column class to defaults

The column class is used by nth-* approaches and needs to be
generated for default styling.
[issues-5] Sets default options using column-policy-options
[issues-5] Adds support for the use once flag in column-policy

This implements the use once flag in the column-policy mixin.
If it is set to true then the custom options will reset back to
the default original options.
[issues-5] Updates documentation to reflect changes in branch
Merge pull request #6 from leadiv/issues-5

Adds support for nth-of-type and nth-child along side data-attributes