#90 - add watchers to issue during issue serialization
Changed the test data to use Redmine 2.5.2 instead of Redmine 2.3.3
Merge pull request #147 from ciasnmic/master

#90 - add watchers to issue during issue serialization
Issue 125. changed Custom Fields to be a Set instead of List
to avoid "duplicate ID" exception when several custom fields
with the same ID are added to the list due to programmer's error.

Closed direct access to CustomFields and other collections in Issue, User and other beans.
User Unmodifiable Collections in Issue and User classes.

Added Fest Assert library to use assertThat() style assertions in tests.
Merge pull request #149 from taskadapter/ask-125-new-duplicate-ids

Issue 125. changed Custom Fields to be a Set instead of List
added some javadoc
Issue 125. changed Custom Fields to be a Set instead of List
to avoid "duplicate ID" exception when several custom fields
with the same ID are added to the list due to programmer's error.

Closed direct access to CustomFields in Issue and User classes.

Added Fest Assert library to use assertThat() style assertions in tests.

Issue 125. changes other elements on Issue to follow the same read-only idea
as  Custom Fields.

made ID final on many beans.
added Factory classes for constructing those beans.

made ID final on more beans.

made ID final on more beans.

made ID final on more beans.

made ID final on more beans.

deleted a useless method
fixed merge errors