Fix invalid string escapes

[notpeelz]

/usr/lib/syncplay/syncplay/utils.py:330: SyntaxWarning: invalid escape sequence '\g'
  return re.sub(constants.ROOM_NAME_STRIP_REGEX, "\g<roomnamebase>", RoomName)
/usr/lib/syncplay/syncplay/utils.py:508: SyntaxWarning: invalid escape sequence '\+'
  CONTROLLED_ROOM_REGEX = re.compile("^\+(.*):(\w{12})$")
/usr/lib/syncplay/syncplay/utils.py:509: SyntaxWarning: invalid escape sequence '\d'
  PASSWORD_REGEX = re.compile("[A-Z]{2}-\d{3}-\d{3}")
/usr/lib/syncplay/syncplay/constants.py:115: SyntaxWarning: invalid escape sequence '\.'
  FILENAME_STRIP_REGEX = "[-~_\.\[\](): ]"
/usr/lib/syncplay/syncplay/constants.py:116: SyntaxWarning: invalid escape sequence '\-'
  CONTROL_PASSWORD_STRIP_REGEX = "[^a-zA-Z0-9\-]"
/usr/lib/syncplay/syncplay/constants.py:117: SyntaxWarning: invalid escape sequence '\+'
  ROOM_NAME_STRIP_REGEX = "^(\+)(?P<roomnamebase>.*)(:)(\w{12})$"
/usr/lib/syncplay/syncplay/constants.py:166: SyntaxWarning: invalid escape sequence '\m'
  MPC64_EXECUTABLES = ["mpc-hc64.exe", "mpc-hc64_nvo.exe", "x64\mpc-hc\shoukaku.exe"]
/usr/lib/syncplay/syncplay/constants.py:305: SyntaxWarning: invalid escape sequence '\.'
  MPLAYER_ANSWER_REGEX = "^ANS_([a-zA-Z_-]+)=(.+)$|^(Exiting)\.\.\. \((.+)\)$"

[Et0h]

Did a quick check and everything seems to run fine for me on the Windows portable build.