Plugin & definition don't need to be executable

These shell scriptlets are only meant to be included by other shell
scripts to set up some variables and a few helper shell functions.
5.6.0RC3
5.6.0RC4
5.3.29
Merge pull request #216 from GrahamCampbell/new

New PHP Versions
Added php 5.4.32 and 5.5.16
Merge pull request #217 from GrahamCampbell/new

Added php 5.4.32 and 5.5.16
Add definition for 5.6.0
Merge pull request #218 from bcremer/add-php-5.6.0-definition

Add definition for 5.6.0
Upgrade xdebug
Merge pull request #220 from GrahamCampbell/xdebug

Upgrade xdebug
Merge branch 'fix-permissions' of https://github.com/gerardroche/php-build into gerardroche-fix-permissions
Fix permissions (-x) on some definition files.
The definition files do not need to be executable anymore.

Update the CONTRIBUTING.md file accordingly.
Added php 5.4.33 and 5.5.17
Merge pull request #226 from GrahamCampbell/new

Added php 5.4.33 and 5.5.17
Add definition for 5.6.1
Update Travis configuration and run-tests.sh script
Merge pull request #227 from mlocher/php-5.6.1

Add definition for 5.6.1
Allow to explicitly specify the downloaded package type.