Merge pull request #29 from McSherry/release

accidentally pushed commit to wrong branch
avoid calling INC/DEC (probably be faster) (contributes to #26)
begin implementing an assembler

Going to need one sooner or later. Might as well start. Plus, it'll be useful in debugging.
methods for encoding
additional encoding/writing methods for the instruction encoder
correction to InstructionEncoder
implements LZ (tested) (closes #26)
test implementation of HLT (contributes to #28)

Couldn't be implemented in the Instructions class as hardware interrupts are separate and only really available to the Executor.
HLT tested (closes #28)
begin implementing conditional jumps (contributes to #27)
adds JZ/JP doc comms/dispatch entries, adds JE impl/doc/dispatch (contributes to #27)
adds CZ/CP/CE impl/docs/dispatches (contributes to #27)
adds JNZ/JNP/JNE impl/docs/dispatches (contributes to #27)
adds CNZ/CNP/CNE impl/docs/dispatches (closes #27)
update versions for new release
Merge branch 'v0.5-alpha' into release