Can't pipe data to csvlint

[rossjones]

It isn't currently possible to pipe data into csvlint on the command line. As a result it isn't possible to use it to compose workflow where one process in the chain is generating csv. For example - proc_that_generates_csv | csvlint

It should probably default to reading from stdin if no argument are supplied, and have a separate 'usage' trigger (--help, -h)