fix for composer to install.
Merge pull request #3 from damiandennis/composerFix

fix for composer to install.
Modified cost calculation
Merge remote-tracking branch 'origin/master'
Added check for the instance of the CartPosition class
Updated README
Added usage examples for getCost() and getCount(), provided better explaination about events
Merge pull request #5 from samdark/patch-1

Added usage examples for getCost() and getCount(), provided better explaination about events
Removed unused variable discounts
Added serialized property
Merge remote-tracking branch 'origin/master'
Added property storeInSession that defines if the cart will be automatically storred in the session
Code style
Added way to customize session component
Added method removeById