version 2.0.5

#4 Add equals and hashCode methods.
#6 Add NotDefined activity.
#7 Add NotifyAdded activity.

version 2.0.4

Add equals and toString method to model classes.
Change the BacklogHttpClient implementation.
Fix the UpdateIssueParameter.

version 2.0.3

Add parameter.
Change http client config.

version 2.0.2

For public release.
Changed the names of HttpClient wrapper and HttpResponse.
Changed internal classes to above package.

version 2.0.1

Fix bugs.