Add -> token
Add COMMENT and STRING
STRING token will be created correctly
行番号の数え方がおかしいのを修正
XFAIL からtest_lexer を取り除いた。
Merge pull request #39 from kmc-jp/testPassingLexerRebased

Test passing lexer rebased
astのインターフェースのデストラクタを実装
Merge pull request #36 from kmc-jp/ast_impl

astのインターフェースのデストラクタを実装
Add basis of Parser class

Add members and constructor of Parser class.
Add is_eof() member
Add advance() member
Add current_type() member
Add current_string() member
Add make_snapshot() member
Add rewind() member
Add parse_symbol() member
Add parse_identifier() member
Add parse_type() member
Add parse_integer_literal() member
Add parse_character_literal() member