Parse bash style args by calling .parse("--name value --name2 value2") i...

Candidate for addressing #42 for parsing CLI style arguments explicitly 

```
scala> class XArgs extends FieldArgs { var x: Int = 3 }
defined class XArgs

scala> val args = new XArgs
args: XArgs = XArgs@7243afc4

scala> args.x
res1: Int = 3

scala> args.parse("--x 17")

scala> args.x
res3: Int = 17
```

still a problem if you have line separated arguments, but I don't think that can be helped

```
scala> :paste
// Entering paste mode (ctrl-D to finish)

args.parse("--x 17 \
--y 18.0")

// Exiting paste mode, now interpreting.

<console>:1: error: invalid escape character
       args.parse("--x 17 \
```

current course of action is to perform `:%s/\\\n//g` first

Also snuck in a typo fix for the readme