Test GROUP_HEREDOC_START_TEST
NAMED_SIGIL tests
Test SIGIL
Optimize test imports
Optimize src imports
Add test for CharList sigil
GROUP test and test optimization
Extract superclass from SigilTest
Generalize org.elixir_lang.elixir_flex_lexer.Test

Make initialState a method instead of a field so that it can be overrode
for YYInitialTest.
Use Test superclass in InterpolationTest
Use Test superclass in GroupHeredocStartTest
Use Test superclass in BodyTest
Use general Test superclass in NAMED_SIGIL tests
Use Test superclass in GROUP_HEREDOC_LIN_START tests
Replace GROUP_HEREDOC_LINE_BODY Test with Test superclass
Use Test superclass in GROUP tests
GROUP_HEREDOC_END tests