Added unit tests for apostrophes used as quotes and free-standing apostrophes

Added unit test to handle apostrophes used as quotes. For example,

`She said, 'let's meet at twelve o'clock'`

And another to handle apostrophes outside of a word, for example between words or within other punctuation.

`go ' Go '' GO`

These tests were added after discussions with several developers working on this exercise.

The example solution was also updated to ensure it passes the new tests.