Use aggregations for pagination, fixes mongodb#437 and mongodb#428

Updated tests for mongodb#414

Fixes mongodb#439

Merge fixes for mongodb#418 and mongodb#439

Merge pull request mongodb#436 from lennynyktyk/mongo30-distinct

Fixed serialization issue when connecting to MongoDB 3.0

Make getQualifiedParentKeyName public

Merge pull request mongodb#421 from jonwhittlestone/fix-readme-softde…

…lete

correct SoftDelete Trait reference

Merge pull request mongodb#421 from jonwhittlestone/fix-readme-softde…

…lete

correct SoftDelete Trait reference

Remove the ext-mongo from composer.json

Add php 5.6 to Travis