cbcTools 0.3.0

This release addresses the following issues: #7 , #9, #10

For #7, I modified code in cbc_design() to avoid duplicate choice sets for the same respondents in random designs.

For #9 and #10, I modified code in cbc_design() to allow Bayesian D-efficient designs with restricted profile sets. I also added some input checks to make sure that the program would stop or throw warnings appropriately if the input settings made it impossible to create a design.