You can tell Composer to autoload any (non-PSR) class by adding the base folder to:
"autoload": {
"classmap": [
"app/commands",
"app/database/migrations",
"app/database/seeds",
"app/tests/TestCase.php"
],
....
And you can also autoload autoloaders by adding them to the files section:
"autoload": {
"files": [
"temboo/src/Temboo_Loader.php"
],
...
After adding those entries, execute
composer dumpautoload
And check the file vendor/composer/autoload_classmap.php
, the available classes must be all listed in it, if one file is not there it will not be autoloaded.