Multiple bold or italic sections in one string are not handled properly

[aantonovich]

String like "test str _first italic section_ some text _second italic section_ some later text" handled like
"test str first italic section_ some text _second italic section some later text"
Same problem related to bold sections.
To fix it regex should be corrected:
Instead of

        // Bold
        .replace(/\*(\S.*)\*/g, '**$1**')
        // Italic
        .replace(/\_(\S.*)\_/g, '*$1*')

Should be

        // Bold
        .replace(/\*(\S[^*]*)\*/g, '**$1**')
        // Italic
        .replace(/\_(\S[^_]*)\_/g, '*$1*')

[FokkeZB]

Excellent. Could you send a pull request?