bundler gem templateに移行

#6 のための変更です

- set VERSION='1.0.0'
- add gemspec, Gemfile, Gemfile.lock, LICENSE.txt
- convert README.rdoc -> README.md
- update .gitignore, Rakefile, Makefile
- delete script/*, History.txt, lib/junk
- move class Gyazz into module Gyazz::Client
- use "minitest" gem for test
- use "httparty" and "httmultiparty" gem to upload image