Started writing lexer for h265. Wrote type Lexer as we required a data struct we can initialize before starting the lexing process, with for example, information regarding the presense of DONL and
DOND. Wrote handler for aggregation packet. Still need to do fragmentation packet.
Added parse.go. This file contains functionality to obtain the Payload from an RTP packet.
Unexported functions to help with this extraction have been added; extHeaderLen, hasExt,
csrcCount and version.