add solution to #1454 to troubleshooting

The solution suggested by Seldaek helped to solve the issue.

https://github.com/composer/composer/issues/1454

doc/articles/troubleshooting.md

@@ -35,6 +35,17 @@ This is a list of common pitfalls on using Composer, and how to avoid them.
    your repository, especially when maintaining a third party fork and using
    `replace`.
 
+## Package not found in travis-ci
+1. Check the trouble shooting for "Package not Found" above
+2. The problem might be that composer is not able to detect the version of the 
+   package properly. If it's a git clone it's alright and it will see the current 
+   branch, but on travis it does shallow clones so that probably fails. The best 
+   solution for travis is to define the version you're on via an environment var 
+   called COMPOSER_ROOT_VERSION. You set it to "dev-master" for example to define 
+   the root package's version as "dev-master".
+   Use: `before_script: COMPOSER_ROOT_VERSION=dev-master composer install` to export
+   the variable for the call to composer
+
 ## Memory limit errors
 
 If composer shows memory errors on some commands: