Improve composer.json

Improve composer.json

Following great article from Jordi: http://seld.be/notes/new-composer-patterns

Changelogs summary:

 - paragonie/random_compat updated from 1.1.1 to 1.1.4
   See changes: https://github.com/paragonie/random_compat/compare/1.1.1...1.1.4
   Release notes: https://github.com/paragonie/random_compat/releases/tag/1.1.4

 - doctrine/cache updated from v1.5.2 to v1.5.4
   See changes: https://github.com/doctrine/cache/compare/v1.5.2...v1.5.4
   Release notes: https://github.com/doctrine/cache/releases/tag/v1.5.4

 - sensio/framework-extra-bundle updated from v3.0.11 to v3.0.12
   See changes: https://github.com/sensiolabs/SensioFrameworkExtraBundle/compare/v3.0.11...v3.0.12
   Release notes: https://github.com/sensiolabs/SensioFrameworkExtraBundle/releases/tag/v3.0.12

 - nelmio/cors-bundle updated from 1.4.0 to 1.4.1
   See changes: https://github.com/nelmio/NelmioCorsBundle/compare/1.4.0...1.4.1
   Release notes: https://github.com/nelmio/NelmioCorsBundle/releases/tag/1.4.1

 - friendsofsymfony/rest-bundle updated from 1.7.4 to 1.7.6
   See changes: https://github.com/FriendsOfSymfony/FOSRestBundle/compare/1.7.4...1.7.6
   Release notes: https://github.com/FriendsOfSymfony/FOSRestBundle/releases/tag/1.7.6

 - nelmio/api-doc-bundle updated from 2.11.0 to 2.11.1
   See changes: https://github.com/nelmio/NelmioApiDocBundle/compare/2.11.0...2.11.1
   Release notes: https://github.com/nelmio/NelmioApiDocBundle/releases/tag/2.11.1

 - neitanod/forceutf8 updated from v1.5 to v2.0
   See changes: https://github.com/neitanod/forceutf8/compare/v1.5...v2.0
   Release notes: https://github.com/neitanod/forceutf8/releases/tag/v2.0

 - j0k3r/graby-site-config updated from 1.0.9 to 1.0.10
   See changes: https://github.com/j0k3r/graby-site-config/compare/1.0.9...1.0.10
   Release notes: https://github.com/j0k3r/graby-site-config/releases/tag/1.0.10

 - j0k3r/graby updated from 1.0.6 to 1.0.7
   See changes: https://github.com/j0k3r/graby/compare/1.0.6...1.0.7
   Release notes: https://github.com/j0k3r/graby/releases/tag/1.0.7

 - sebastian/diff updated from 1.4.0 to 1.4.1
   See changes: https://github.com/sebastianbergmann/diff/compare/1.4.0...1.4.1
   Release notes: https://github.com/sebastianbergmann/diff/releases/tag/1.4.1

 - phpunit/phpunit updated from 4.8.19 to 4.8.21
   See changes: https://github.com/sebastianbergmann/phpunit/compare/4.8.19...4.8.21
   Release notes: https://github.com/sebastianbergmann/phpunit/releases/tag/4.8.21

 - kphoen/rulerz updated from 0.16.1 to 0.16.2
   See changes: https://github.com/K-Phoen/rulerz/compare/0.16.1...0.16.2
   Release notes: https://github.com/K-Phoen/rulerz/releases/tag/0.16.2