V2.0 update

## Features 

### Open
* Now returns the activeDocument after opening the file.

### JSLayer()
* Removed semicolon from output.

### Document
* Added FullName() which returns path to the .psd file.
* Changed Filename() to DumpFile(), as Filename was misleading.
* Dump function now saves the file as well,
to help reduce the frequency of de-syncs.
* Dump function now saves json files alongside the .psds
instead of in a separate data folder- encountered issues when using
the package as a module in go 1.11beta2.
* Added Save()

## Testing
* Added TestDocument_Save
* Added TestDocument_Dump

## Misc.
* Renamed pkgpath to pkgPath, to better fit go's standards.

## Fixes
* DoAction now runs correctly.

layerset.go

@@ -201,8 +201,7 @@ func (l *LayerSet) SetVisible(b bool) error {
 	if l.visible == b {
 		return nil
 	}
-	js := fmt.Sprintf("%s.visible=%v;", strings.TrimRight(
-		JSLayer(l.Path()), ";"), b)
+	js := fmt.Sprintf("%s.visible=%v;", JSLayer(l.Path()), b)
 	if _, err := DoJS("compilejs.jsx", js); err != nil {
 		return err
 	}
@@ -297,10 +296,3 @@ func (l *LayerSet) Refresh() error {
 	l.current = true
 	return nil
 }
-
-func (l *LayerSet) Set(ll *LayerSet) {
-	if ll == nil {
-		panic("AHHHHHH")
-	}
-	l = ll
-}