add ConstantDict definition
add test utilities with EnhancedTestCase and use it in all tests, add tests for ConstantDict
fix remark
bump version
Merge branch 'master' into ConstantDict

Conflicts:
	test/missing.py
replace ConstantDict with FrozenDictKnownKeys, update unit tests
Merge branch 'master' into ConstantDict

Conflicts:
	test/fancylogger.py
	test/missing.py
add frozendict module
fix conflict resolution
resolve remarks and enhance unit tests
raise KeyError for unknown keys, and check KeyError in unit tests
only use EnhancedTestCase where actually useful
remove unneeded import
Merge pull request #107 from boegel/ConstantDict

add ConstantDict and enhance unit tests