Progressive filtering modification

[turnerniles]

Upon filtering sets originalArgs.data equal to the filtered data which is then used in successive filter method calls.

This naming is confusing since originalArgs.data will not always contain the originalArgs and will contain the "filteredArgs" but I don't think we need to add an additional filteredArgs property to the Pivot class. this.originalData is also set equal to the result of the filtered data in the update method so perhaps we should consider renaming originalArgs and originalData.

[coveralls]

Coverage increased (+0.006%) to 98.624% when pulling 4908341 on progressive-filtering-modification into ee28233 on master.

[coveralls]

Coverage increased (+0.006%) to 98.624% when pulling 0a4bbf4 on progressive-filtering-modification into ee28233 on master.

[coveralls]

Coverage increased (+0.006%) to 98.624% when pulling 482103d on progressive-filtering-modification into ee28233 on master.

[coveralls]

Coverage increased (+0.006%) to 98.624% when pulling 4d7e399 on progressive-filtering-modification into ee28233 on master.

[coveralls]

Coverage increased (+0.006%) to 98.624% when pulling f089438 on progressive-filtering-modification into ee28233 on master.

[pat310]

Looks great