fix exceptions inheritance

Traceback (most recent call last):
  File "./jenkins.py", line 12, in <module>
    print(jenkins[jobName].get_scm_type())
  File "build/bdist.freebsd-9.2-STABLE-amd64/egg/jenkinsapi/job.py", line 324, in get_scm_type
NameError: global name 'exceptions' is not defined
Merge pull request #172 from kworr/patch-1

fix exceptions inheritance
Raise NoBuildData when latestBuild etc. not even set

The Folders plugin uses jobs as a container for folders.
However, a lot of standard job keys, such as lastBuild et al.
are not even present (unlike a never run job where they are
present but set to None)

Since a value of None for latestBuild causes a NoBuildData
exception, the same exception should be fine when not present.
Merge branch 'folders_plugin_fix' of https://github.com/willthames/jenkinsapi into unstable