Add CacheManager tests.

[allenh1]

Adds testing for CacheManger.py.

$ coverage run --source=superflore -m nose && coverage report -m
..................................................
----------------------------------------------------------------------
Ran 50 tests in 13.437s

OK
Name                                               Stmts   Miss  Cover   Missing
--------------------------------------------------------------------------------
superflore/CacheManager.py                            20      0   100%
superflore/PackageMetadata.py                         22      0   100%
superflore/TempfileManager.py                         34      6    82%   48-56
superflore/__init__.py                                10      4    60%   5-8
superflore/docker.py                                  51     12    76%   40, 54-67, 77, 80-81
superflore/exceptions.py                              18      3    83%   28, 33, 38
superflore/generate_installers.py                     63      0   100%
superflore/generators/__init__.py                      0      0   100%
superflore/generators/bitbake/__init__.py              3      1    67%   3
superflore/generators/bitbake/gen_packages.py        102     79    23%   40-122, 129-168, 175-183, 189
superflore/generators/bitbake/ros_meta.py             27     18    33%   24-27, 30-35, 38-51, 54-55
superflore/generators/bitbake/run.py                 113     90    20%   43-187
superflore/generators/bitbake/yocto_recipe.py        120    100    17%   44-67, 70, 73-77, 80-92, 95-99, 102-104, 107-108, 116-119, 128-187
superflore/generators/ebuild/__init__.py               3      1    67%   3
superflore/generators/ebuild/ebuild.py               185     19    90%   96-99, 126-131, 146, 176-180, 186, 193, 206-210
superflore/generators/ebuild/gen_packages.py         140    113    19%   46-119, 125-137, 143-188, 193-210, 213, 216
superflore/generators/ebuild/metadata_xml.py          33      0   100%
superflore/generators/ebuild/overlay_instance.py      35     24    31%   26-31, 34-45, 50-69, 72-73
superflore/generators/ebuild/run.py                  121     95    21%   48-188, 192-196
superflore/parser.py                                  13      0   100%
superflore/repo_instance.py                           70     51    27%   29-49, 56-65, 68-76, 82-83, 89, 95-96, 102, 105-120, 123
superflore/rosdep_support.py                          34      2    94%   83-84
superflore/test_integration/__init__.py                0      0   100%
superflore/test_integration/gentoo/__init__.py         3      1    67%   3
superflore/test_integration/gentoo/build_base.py      26     17    35%   26-28, 33, 38-50
superflore/test_integration/gentoo/main.py            30     24    20%   26-71
superflore/utils.py                                  189     67    65%   50-56, 60-63, 67-82, 86-97, 101-104, 114, 174, 191-194, 196, 202, 208-209, 214, 218-219, 226-247
--------------------------------------------------------------------------------
TOTAL                                               1465    727    50%

[tfoote]

50% coverage!