Adjust specs for String#eql?, String#==
Share specs for String#===
Fix String#bytes when no block given
Merge pull request #201 from kachick/write-spec-string-case_compare

Share specs for String#===
Merge pull request #202 from kachick/fix-string-bytes

Fix String#bytes when no block given
Add specs for Kernel#instance_variable_set when self is frozen