Improved specs for webservice

* webservice class is now 100% covered
Fix some bug in Webservice class

*Fix typo
*Fix documentation
*Fix function
Improve MagentoItemStepSpec #191
Merge pull request #192 from akeneo/enhancement/specMagentoItemStep

Improve MagentoItemStepSpec #191
Merge branch 'master' into enhancement/improve-specs
Merge branch 'enhancement/improve-specs' of github.com:akeneo/MagentoConnectorBundle into enhancement/improve-specs