Removed escript file as option

It is gernally better to just use the parse transform. Using the
escript still required rec2json as a dependancy, and using raw
records to make modules just meant they were harder to extend later.
Further, the script increased the steps in a compile. Using a parse
transform is just plain better.
Compile options to be compatable with rebar defined parse_transform
Added option to control accessors
De-emphasizing the script, and prmoting parse trans.
Merge branch 'master' of https://github.com/hairyhum/rec2json into hairyhum-master
Supressig accessor creation on scan_string works.
Added tests for conditional accessor generation
Added documentation about gernate_accessors
Merge branch 'hairyhum-master'