Generic sh-elf target support.
Add a contribution information file
Emphasis commands
re-formulate some sentences
Merge pull request #474 from monaka/pr-generic-sh-elf-support

Generic sh-elf target support.
Merge pull request #475 from bovi/contributing

More Contributing Documentation
OP_CALL for cfunc must restore callinfo; close #476
Merge branch 'master' of github.com:mruby/mruby
should adjust pc after OP_CALL
should not call mrb_parser_free() on NULL pointer
load_exec should return undef on syntax errors
should adjust array size
mrb_long2int(n) : Remove as unused.
defines.h : Remove as already commented out.
Remove extern mrb_top_self. It is declared in mruby.h.
mruby should exit with 0 on success
wrong termination of mrb_run on exception; close #480
Merge pull request #481 from monaka/pr-tiny-cleanup-20120929

Tiny clean-up
add test case for Array#unshift, <=>, and *
Merge pull request #483 from akuroda/array_test

add test cases for Array
should handle exception from Ruby implemented method called from funcall; close #484