Fixing loading error on rbenv

Hello,

when using rbenv (or when do you "rb" string within your path) the rubygem refused to load for obvious reasons:

```
[root@localhost smart-proxy]# ruby -rrubyipmi -e true
/root/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rubyipmi-0.5.0/lib/rubyipmi/ipmitool/commands/bmc.rb
/root/
/root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- /root/ (LoadError)
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rubyipmi-0.5.0/lib/rubyipmi/ipmitool/connection.rb:9:in `block in <top (required)>'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rubyipmi-0.5.0/lib/rubyipmi/ipmitool/connection.rb:6:in `each'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rubyipmi-0.5.0/lib/rubyipmi/ipmitool/connection.rb:6:in `<top (required)>'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rubyipmi-0.5.0/lib/rubyipmi.rb:1:in `<top (required)>'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:60:in `require'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:60:in `rescue in require'
	from /root/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/rubygems/custom_require.rb:35:in `require'
```

I don't understand why do you split the string as Ruby 1.8-2.0 loads files with extensions fine. Thus sending the fix.

Take care!