It seems to be a neologism. `wordreference.com` isn't referencing this word but [un-installation](http://www.wordreference.com/enfr/un%20installation). 
However articles do [Wikipedia Uninstaller](http://en.wikipedia.org/wiki/Uninstaller).

Btw, as we say `installer` => `installation`, it seems correct to have `uninstaller` => `uninstallation`