Add some examples and rename file
Add the function which adds example in a buffer and some change.

rename eval-string -> ex-eval-string

Add utility function:
ex-insert-current-buffer -  "Insert example code snippet like (ex-put-exmaple 'car '(\"(car '(1 2 3))\"))"
ex-delete-last-elem - delete last element in function examples
Add move test file.