Docs: init process for existing RSpec project
Docs: init process for existing RSpec project

If you run `awspec` on a RSpec project that has already been initialized, it will fail with something like:

```
$ awspec init
!! spec/spec_helper.rb already exists
 + Rakefile
 + spec/.gitignore
!! .rspec already exists
```
k1LoW/awspec,k1LoW/awspec