Merge pull request #7 from mkreyman/65851752_about_strings_master

about strings master

[Delivers #65851752]
Fixed about_hashes.rb to pass all tests

Learned about:
- creating hashes,
- hash literals,
- various ways to access and modify values in hashes,
- testing hash keys,
- combining hashes,
- default values when creating a new hash,
- that a block can be passed as a default value for new hash.

[#65851750]