First version of abalone dataset research md file

Testing the rendering of attribute info table.
Added dataset history to clara_abalone.md, fleshed out the structure and contents section, and added a code block to describe how to acquire the data.
Added data summary to clara_abalone.md
Updated data summary section of clara_abalone.md with neater tables.
Added past usage information to clara_abalone.md.
Merge pull request #49 from csojinb/master

(Clara) Abalone dataset research Thanks!