Update 03-basic-crud.markdown

Added a note that calls to find* methods do not always set off database queries and how to avoid that, if necessary.
Update 03-basic-crud.markdown

Moved the tip to an extended information block about the instance pool and when it is consulted.
Update 03-basic-crud.markdown

Changed findOneById to findOneByXXX magic method for primary key attributes
Merge pull request #211 from carlwitt/patch-1

Update 03-basic-crud.markdown