* check field reg.
 * rm ie6 codes.
 * fix switchstatus function.
 * Fix fields number.
 * adjust field use pattern.
 * add php extension on wechatlog file.
 * modify link function of tag module.
 * Add 2.5.1 .
 * upgrade version to 2.5.2.
 * Change summary to desc.
 * add wwwroot.
 * fix tw lang.
 + import the htmlpurifier class.
 * apply the htmlpuifier logic to striptags.
 * fix wwwroot.
 * Add switch purfy param.
 * Add 2.5.2 chanzgelog