Paragraph headers always end in a period

[shinnar]

Paragraph headers are always ended in a period, even if they end in a punctuation.

This is due to

\titleformat{\paragraph}[runin]%
            {\bfseries\normalsize}%
            {}%
            {0.5em}%
            {}%
            [.]%

Using the amsmath package, I can fix this by changing it to

\titleformat{\paragraph}[runin]%
            {\bfseries\normalsize}%
            {}%
            {0.5em}%
            {}%
            [\@addpunct{.}]%

I would submit a PR, but am not sure if the dependency on amsmath is reasonable.

[rmgarnett]

It would be easy to simply borrow the definition of \@addpunct from amsmath.