Adapt to CRAN policies.

Omit NA in list. (#35)

Update DESCRIPTION and update version to 0.1.8

Update to version 0.1.7

Update to version 0.1.6

Update to version 0.1.5

Update to version 0.1.4

Update version to 0.1.3

Update version to 0.1.2

FIX: error in count (A & B & !C & D) part. (#3)

* Adapt to using 'data.table'.
* Add code to check such typos.
* Update version to 0.1.1