Money#parseString throws NotImplementedError

[vlovgr]

import squants.market._

Money.parseString("1000 USD")
// scala.NotImplementedError: an implementation is missing

[hunterpayne]

Add this to the Money object in Money.scala:

override def parseString(s: String): Try[Money] = apply(s)

Then add this to MoneySpec.scala:

it should "handle round trip parsing of money as a string" in {
// Issue #321
val money = Money(1000d, USD)
Money(money.toString)
// Issue #322
Money.parseString("1000 USD")
}

Make sure it all works on your end, then submit a PR...