v0.2.1

• new functions or methods mul!, resize!, zz2vector, zz2vector!, count_zeros, count_ones
• accept more general second argument for matrix multiplication
• overload LinearAlgebra.rank instead of separate rank function
• added faster convert to and from BitVector
• fixed padding bug for 0-length arrays, added test for negative dimensions for ZZ2Array
• added tests and fixed bug in runtests.jl
• added documentation