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

workaround

another todo comment

fix nonsense

expand as necessary thing

add [ and ] to test thing

implement [ and ]

untested

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

go fmt

handle errors from Step function

errors stuff

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