Codeception 2.1 dev branch installation phpunit requirements - symfony

Question

I'm trying to install the codeception dev branch of 2.1.x for my Symfony project. Using composer, its unable to match the requirements:
[01:36 PM]-[root#oracle]-[~]
# phpunit --version
PHPUnit 4.8.11 by Sebastian Bergmann and contributors.
[02:03 PM]-[vagrant#oracle]-[/var/www]-[svn]
$ composer require --dev "codeception/codeception:2.1.3"
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.
Problem 1
- Installation request for codeception/codeception 2.1.3 -> satisfiable by codeception/codeception[2.1.3].
- Conclusion: don't install phpunit/phpunit 4.8.11
- Conclusion: don't install phpunit/phpunit 4.8.10
- Conclusion: don't install phpunit/phpunit 4.8.9
- Conclusion: don't install phpunit/phpunit 4.8.8
- Conclusion: don't install phpunit/phpunit 4.8.7
- Conclusion: don't install phpunit/phpunit 4.8.6
- Conclusion: don't install phpunit/phpunit 4.8.5
- Conclusion: don't install phpunit/phpunit 4.8.4
- Conclusion: don't install phpunit/phpunit 4.8.3
- Conclusion: don't install phpunit/phpunit 4.8.2
- Can only install one of: phpunit/phpunit[4.8.0, 4.6.6].
- Can only install one of: phpunit/phpunit[4.8.0, 4.6.6].
- Can only install one of: phpunit/phpunit[4.8.0, 4.6.6].
- codeception/codeception 2.1.3 requires phpunit/phpunit ~4.8.0 -> satisfiable by phpunit/phpunit[4.8.0, 4.8.1, 4.8.10, 4.8.11, 4.8.2, 4.8.3, 4.8.4, 4.8.5, 4.8.6, 4.8.7, 4.8.8, 4.8.9].
- Conclusion: don't install phpunit/phpunit 4.8.1
- Installation request for phpunit/phpunit == 4.6.6.0 -> satisfiable by phpunit/phpunit[4.6.6].
Installation failed, reverting ./composer.json to its original content.
Strangely after this, phpunit somehow downgrades to version 4.6.6
$ phpunit --version
==== Redirecting to composer installed version in vendor/phpunit ====
PHPUnit 4.6.6 by Sebastian Bergmann and contributors.
Note I'm currently using CentOS 6.5 in a vagrant environment.
EDIT: composer.json
require: {
"php": ">=5.3.3",
"phpunit/phpunit": "4.6.*",
"symfony/symfony": "~2.4",
"doctrine/orm": "2.4.*",
"doctrine/doctrine-bundle": "~1.2",
"twig/extensions": "~1.0",
"symfony/assetic-bundle": "~2.3",
"symfony/swiftmailer-bundle": "~2.3",
"symfony/monolog-bundle": "~2.4",
"sensio/distribution-bundle": "~2.3",
"sensio/framework-extra-bundle": "~3.0",
"sensio/generator-bundle": "~2.3",
"incenteev/composer-parameter-handler": "~2.0",
"braincrafted/bootstrap-bundle": "~2.0",
"twbs/bootstrap": "3.0.*",
"jquery/jquery": "1.10.*",
"components/jqueryui": "1.11.*",
"components/modernizr": "*",
"knplabs/knp-menu": "~2.0#alpha",
"knplabs/knp-menu-bundle": "~2.0#alpha",
"knplabs/knp-paginator-bundle": "dev-master",
"kuleuven/shibboleth-bundle": "dev-master",
"liip/functional-test-bundle": "~1.0",
"leaseweb/api-caller-bundle": "*",
"pdepend/pdepend": "~2.0",
"FortAwesome/Font-Awesome": "*",
"brown298/data-tables-bundle": "0.4.*",
"ircmaxell/password-compat": "~1.0.3",
"doctrine/doctrine-fixtures-bundle": "2.2.*",
"mmoreram/controller-extra-bundle": "1.0.*#dev"
}