Fixes #483: Update dependencies for php 5.5 during composer install

[greg-1-anderson]

Overview

This pull request:

• Fixes a bug
• Adds a feature
• Breaks backwards compatibility
• Needs tests

Description

Allows composer install to work out-of-the-box with php 5.5. Detects a composer.lock file containing incompatible dependencies, and fixes up the composer.json require-dev section as needed.

n.b. Simply removing composer.lock does not do the trick. Seems like it should, but it doesn't.

As a bonus, this PR also adds highest / lowest dependency checking to Robo tests.

[coveralls]

Coverage decreased (-0.2%) to 58.362% when pulling b9327a9 on php-55-checks into 3530d52 on master.

[coveralls]

Coverage decreased (-0.2%) to 58.362% when pulling b9327a9 on php-55-checks into 3530d52 on master.

[coveralls]

Coverage decreased (-0.2%) to 58.362% when pulling b9327a9 on php-55-checks into 3530d52 on master.

[coveralls]

Coverage remained the same at 58.526% when pulling b9327a9 on php-55-checks into 3530d52 on master.

[coveralls]

Coverage remained the same at 58.526% when pulling 3ed19c7 on php-55-checks into 3530d52 on master.

[coveralls]

Coverage increased (+0.008%) to 58.535% when pulling adf3893 on php-55-checks into 3530d52 on master.

[coveralls]

Coverage increased (+0.008%) to 58.535% when pulling adf3893 on php-55-checks into 3530d52 on master.