Fix: typo comand
Merge pull request #52 from u16suzu/fix_typo_readme

Fix: typo at readme
Allow RDoc ~> 4.0.0.rc
First pass to make sdoc work with RDoc 4

These are the bare minimum required changes to make the generator pass without errors. Some
things still not working:

* Github link now showing up
* Code blocks not working correctly (using Markdown)
* Probably more errors
bump rdoc to released 4.0.0
default to RDoc::Options#pipe = true
add Gemfile, just points to sdoc.gemspec
add development dependencies
remove rspec task and add rake testtask
added specs for SDoc::Generator using MiniTest::Spec::DSL with RDoc::TestCase
update .gitignore
fixed search index option with @KevinSjoberg
search index option template name changed