Add matrix Redis datatype
Add test for xset
Add matrix print function for debug

Prints a matrix's attributes to stdout for debugging
Copy values when setting XSETing
Improve some code readability
Make XGET return subregion of matrix

Replies with:

* Number of dimensions (dims)
* dims replies for the size of each dimension (shape)
* product(shape) replies for each value
reformat matrixPrint function body
Move getReshapedIndex to top of file
Don't need to memcpy dims
Store size on matrix struct

Seems like I'm recomputing this number all over the place
Remove unused variable
Reformat matrixSlice
Make shape memcpy simpler (to me)
Box values in scalar struct for ref counting
Add zero matrix function for initializing with zeros
Slice and set values in subregion
Remove unused function
Add XZEROS and XONES for creating matrices
Reorganize function declaration order
Inline variable declaration and initialization