Fix documentation

Allow links and screenshots to work in Atom.
I thought I could be clever and just link to the files in the repo and have Atom display the local versions, but unfortunately that isn't supported.

README.md

@@ -27,13 +27,13 @@ Did you not like the look of the Arduino IDE but were stuck with it nevertheless
 * `arduino-upload:upload` - Uploads the current sketch to a connected arduino
 * `arduino-upload:serial-monitor` - Opens the serial monitor of a connected arduino
 
-You can place these commands in a toolbar using the [**Flex Tool Bar**](https://atom.io/packages/flex-tool-bar) package. [Here's how](docs/toolbar.md).
+You can place these commands in a toolbar using the [**Flex Tool Bar**](https://atom.io/packages/flex-tool-bar) package. [Here's how](https://github.com/Sorunome/arduino-upload/blob/master/docs/toolbar.md).
 
 ## Screenshots
 Verifying a program:
 
-![verify](docs/screenshots/verify.gif)
+![verify.gif](https://raw.githubusercontent.com/Sorunome/arduino-upload/master/docs/screenshots/verify.gif)
 
 Serial monitor:
 
-![serial](docs/screenshots/serial.gif)
+![serial.gif](https://raw.githubusercontent.com/Sorunome/arduino-upload/master/docs/screenshots/serial.gif)