First release with T_* tokens - Breaks v0.8.0

v0.90 contains breaking changes from v0.8.0, specifically:

• Renaming TokenType* built-in tokens (i.e. "TokenTypeEOF") to T_* (i.e "T_EOF")
• Changing the value of the built-in EOF token from -1 to 0

A few other changes were added but not have been thoroughly tested so I'm marking this release as beta for now.

Tagging a release for Go module support

Tagging a v0.8.0 release so I can use this package in Go modules. I believe this release to be pretty stable, but am generally reluctant to call anything v1 or beyond unless I've been using it a lot in recent projects.