Move the note to the top of the readme and rename some sections
Use more semantic headings (subheadings should be one tier smaller)
Remove empty newlines after headings
Reorganize the "Compiling" section
Simplify first heading and move parts of it into the description
Remove the full license text from the readme
Merge pull request #66 from nicolasmccurdy/readme-edits

Readme edits
Improve yyerror messages

Syntax error messages should show position of the error.
Add line number information and the error token.