Fix build for 17.0 using the solutiong proposed by @tsloughter

We use namespaced_types option to choose between dict() and dict:dict() types.
Add namespaced_types to bootstrap script.
Add erlang 17.0 to travis
Merge pull request #292 from matwey/namespaced_types

Namespaced types: fix build for 17.0
Add {prefix, atom()} option for abnfc_opts

Specify the atom to use as a prefix for the decoder and generator
functions inside the parser's module.  Default is ''.
Add {parser, module()} option for abnfc_opts

Specify the module to use for parsing the ABNF grammars.  Default is
'abnfc_rfc4234'.
Add {qc, proplist()} option for abnfc_opts

Specify the options to use for the generator functions inside the
parser's module.  Default is [].