Remove implicit namespacing

This removes the unnecessary `EC*Fp` prefix/suffixes on the two classes in the project.
A typical use case:

```
var ecurve = require('ecurve')

ecurve.Point.decodeFrom(myCurve, someBytes)
```

If they omit the `ecurve` for convenience, then, it is understood that they are throwing away the namespacing information.  No need to double up.