Fix minor issues

- Force output by Default Encoding
- Reject Executing path is begin with UNC path
- There is no need to convert to UTF8 after Uri.EscapeDataString
- Fix commands 'ls -la' will execute 'ls' and 'la' issue, and now, it will split by '\n'

TODO: if commands contains '\\\n' it may occur an error, so it need to replace by ' ', and needs to confirm
Merge pull request #3 from rjeczalik/stderr-fix

Fix for reading process' stderr
Merge pull request #2 from Haraguroicha/master

Fix minor issues