ATOM – A hackable text editor
Atom works across operating systems. You can use it on OS X, Windows, or Linux.
Built-in package manager
Search for and install new packages or start creating your own—all from within Atom.
Atom helps you write code faster with a smart, flexible autocomplete.
File system browser
Easily browse and open a single file, a whole project, or multiple projects in one window.
Split your Atom interface into multiple panes to compare and edit code across files.
Find and replace
Find, preview, and replace text as you type in a file or across all your projects.
Install ATOM on Ubuntu 15.04
You need to download .deb package from here .Once you have deb package you can double click on it to install
Check ATOM Documentation how to use and hack.