require https instead of http to resolve undefined use_ssl= error in ruby 1.8

In Ruby 1.8, I keep getting this error when installing gem.
```
$ rbenv global 1.8.7-p352
$ gem install rspec
Fetching: rspec-core-2.14.8.gem (100%)
ERROR:  While executing gem ... (NoMethodError)
    undefined method `use_ssl=' for #<Net::HTTP github.com:443 open=false>
```
We should require https instead of http so that the method use_ssl= will be available in ruby 1.8.