Fix to pass tests and add primitive tests for ImmutableValue

Signed-off-by: Tsuyoshi Ozawa <ozawa.tsuyoshi@gmail.com>
Fix assertValueType to assert ValueType#isXxxValue

Signed-off-by: Tsuyoshi Ozawa <ozawa.tsuyoshi@gmail.com>
Add test for isXxxValue

Signed-off-by: Tsuyoshi Ozawa <ozawa.tsuyoshi@gmail.com>
Add isRawValue/isNumberValue tests

Signed-off-by: Tsuyoshi Ozawa <ozawa.tsuyoshi@gmail.com>
Merge pull request #78 from oza/fix-test-and-add-testimmutablevalue

Fix test and add TestImmutableValue