Modified: Support split of tag.
Modified: Support variable length tag.
Modified: Incorporation of comment opinions.
Modified: Raise error if using tag of range.
Modified: Update tag placeholder section.
Modified: Replace from tag to tags. (I failed of typo).
Merge pull request #8 from futoase/support-split-of-tag

Enhanced placeholder like ${tags[n]} which adds part of tag splitting by dot without any settings. Thanks @futoase !

**example**
`apache.access` tag would be resolved like below.
${tags[0]} => apache
${tags[1]} => access

**note**
This function has added as default behavior.