add getDisplayModeBufferSize
Support all Blackmagic video modes

adds getDisplayMode for retrieving correct display mode
adds getDisplayModeBufferSize for retrieving correct buffer size
remove alternative framerate options

removes option to pass 23 for 23.98, or 29 for 29.97
fixes two missed 2398 framerates
Merge pull request #4 from acarabott/modefix

Support all Blackmagic display modes