Update SideBarItem.py

Fix for **Open/Run**.
`open -a` opens with the specified application but we just need it to open with the default application, so the `-a` flag is not needed.
Merge pull request #85 from 0kb/patch-1

Update SideBarItem.py
Update readme.md
fixes #86
add correct chromium run command for ubuntu
Fixed markdown

Fixed the markdown code for the inline screenshot and removed repetition.
Merge pull request #89 from joao/patch-1

Fixed markdown
Merge pull request #88 from devoto13/master

Add correct Chromium run command for Ubuntu
Update readme