added PHP and UTF-8 section
declared utf charset in the connection string

Also updated code example to match phpbestpractices.org example
bump first argument down a line so the example is PSR-2
made utf8mb4 consistently represented as code
removed sentence as wording seemed a little too aggressive
moved inline links to Further Reading section
changed wording so it speaks to code example in this section
fixed word wrapping (now 120 chars)

Also added note about default encoding for htmlentities and
htmlspecialchars and added link to php docs for htmlspecialchars
Merge pull request #358 from ylynfatt/utf-8-section

added PHP and UTF-8 section