add expandAsNecessary to end
fix regex

no idea why it doesn't work, but this works
use actual filename to read from
remove idea comment

no longer needed
remove input

makes testing difficult
another todo comment
expand as necessary thing
add [ and ] to test thing
implement [ and ]

limit memory pointer to size of tape
tiny bug fix

end of code detected too late, out of bounds error
graceful error handling in ,
refactor < instruction
handle errors from Step function
fix nothing used error

nothing is used so nothing is needed
refactor Step function

- step function part of ProgramState
- current memory now has a dedicated variable
- now relies on ProgramState for stuff like code