invalid nodejs titles can lead to illegal project names

[fehguy]

Description

Per https://docs.npmjs.com/files/package.json#name, the title of a project is constrained to certain characters. Currently the codegen will let essentially anything go into the name, with the exception of replacing some underscores to dashes. Needs to be more aggressive and adhere to the npm naming policy

Swagger-codegen version

2.2.2-SNAPSHOT

[wing328]

Should be fixed by #4648