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.

examples_test.go

@@ -6,5 +6,5 @@ func ExampleJSLayer() {
 	// The path of a layer inside a top level group.
 	path := "Group 1/Layer 1"
 	fmt.Println(JSLayer(path))
-	// Output: app.activeDocument.layerSets.getByName('Group 1').artLayers.getByName('Layer 1');
+	// Output: app.activeDocument.layerSets.getByName('Group 1').artLayers.getByName('Layer 1')
 }