fix special characters escaping

[zenovich]

No description provided.

[k1w1]

Thanks for the pull request. I originally disabled the escape_special_characters method because it escapes all special characters, even if they would not be interpreted as special by JIRA markup. This caused frustration for JIRA users because they didn't like the additional backslashes that showed up in the markup. To reenable this escaping we need a more sophisticated algorithm that only escapes when necessary, i.e. when the character would otherwise be confused for markup.

[zenovich]

Have you tried the patch? We successfully migrated all tasks from dobambam.com to Jira converting all texts from HTML to Confluence through patched html2confluence and it escaped characters only when necessary.