parser: implement basic dosini parsing

Signed-off-by: Alejandro Mery <amery@jpi.io>

parser/parser.go

@@ -70,6 +70,10 @@ func (p *Parser) emitError(content string, err error) (lexer.StateFn, error) {
 	}
 }
 
+func (p *Parser) emitInvalidRune(r rune) (lexer.StateFn, error) {
+	return p.emitError(string([]rune{r}), lexer.ErrUnacceptableRune)
+}
+
 // stepLine discards the data and moves the position
 // to the next line.
 func (p *Parser) stepLine() {