Adds ReadContext/WriteContext methods to endpoints and to streams. Update rawread example tool to use ReadContext for implementation of "timeout" flag.
* fix mispell
* update golint path in travis
* Golint requires Go 1.9 or later
* install golint only if go >=1.9
* exclude go 1.7 and go 1.8 for golint
* add build on go 1.10.x
Defines a WriteStream structure for buffering writes, similar to the existing ReadStream. WriteStreams can be created on OutEndpoints by using ep.NewStream().
