Support unicode identifier

Refer to https://javacc.java.net/doc/JavaCC.html, so add JavaCC license
to THIRD-PARTY.
Add tests for feature of unicode identifiers
Fix license format for Markdown (#220)
Wrap text and remove comment (#220)

Wrap text over multiple lines and remove comment to refer JavaCC doc
suggested by @jponge
Merge branch 'unicode-identifier' of git://github.com/MakeNowJust/golo-lang into pr/unicode

Conflicts:
	src/main/jjtree/Golo.jjt
Merge branch 'pr/unicode'

Closes #220