0.8.0: added 'img' support

Added 'img' support. See #22

Improved cache & Allow toXML to be called sync

• Improved internal cache. See #10
• Allow toXML to be called sync. See #11

lastmodISO property to SitemapItem

• added lastmodISO property to SitemapItem. See #9

Added method for remove page

• Added method for remove page. #3
• Added support for minutes/seconds/timezone in lastmod (via lastmodrealtime). #8

Bug fixes

• A lot of bug fixes #7

Sitemap Index

• #6 Added createSitemapIndex