Dimitrios Savvopoulos, the creator of the laravel-translatable package (which I use in almost every project), shared a very nice tip on how to develop a package while it is installed as a requirement.

If you have write access to a composer package repository, you have the possibility to continue its development while it is installed as requirement in another project. Let's see how we can accomplish this.

http://dimsav.com/blog/9/git-repository-inside-composer-vendors

If you have another, possibly better, way to go about this, let me know in the comments.