support buffered printing mode

[gabrielgrant]

as discussed in #2: AFAICT it seems this lib assumes operation is in "Concurrent printing" mode (which seems to be the default over USB), but when connected over bluetooth, the printer seems to operate in "Buffered printing" mode. Would be good to support that too. See #2 for more details

[NotAFile]

Hi, getting back to this now sorry.

I don't see any exact explanation of what this entails in brother's documentation, do you have any more information?

[gabrielgrant]

Hey, sorry for my delayed reply this time :P

From page 39 of the PT-H500/PT-P700/PT-E500 command reference:

Normally, printing is performed as buffered printing.
However, if the printer is connected via USB and uncompressed data is received, concurrent printing is
performed.

It goes on to show flow charts of how both modes work