add error message on invalid register
tweak comments
remove assembler from future work
remove unused fibo files
remove reference to incorrect J type encoding

It turns out I was actually using the same encoding as RARs after all.
Also, as described in the relevant issue on the RARs repo, it was the
correct style all along.
get fibo test case working
assemble lw and sw
assemble branches
implement label resolution
got J types working, I think?

Either I am very confused, or RARS has at least one problem with it's J
type encoding, which means that riscv.awk disagrees with it (which also
breaks the relevant test cases). I have reported the issue upstream
here: https://github.com/TheThirdOne/rars/issues/89
assemble I, R, and shift types
start sketching out the assembler
add link to public inbox
update README, add demo
implement dimp directive
implement lw and sw
add conditional branch instructions