Merge pull request #162 from KeenS/hotfix

fix bug of `{bytevector, vector}-copy!` with the same src and dst
read rational '123/456' literal
'make tak' broken
add pic_dict_new
add attribute information to closure objects
add attribute function
Merge branch 'closure-attribute'. close #124
remove get_var_from_proc (essentially the same as pic_unwrap_var)
remove var accessor and mutators
add pic_funcall
don't use pic_defvar
get rid of doubled semicolons
improve error message
refactor var. c api no longer supports converters.
add pic_set_c[ad]r
manage values in a stack
refactor parameterize
Merge branch 'refactor-var'
add dictionary operators
rename 'dictionary' 'make-dictionary'