support username/password in URL

given that the URL is structured like:

http://username:password@hostname.example.com

use that username/password combination rather than requiring explicit
:username and :password options in the JenkinsApi::Client initializer.
added some comments to document
Leave functional tests out of travis for now.
Merge pull request #118 from spikegrobstein/feature/read-credentials-from-url

read username/password from server_url
Fixed the user unit spec.
Updated .travis.yml.
Cleanup and speedup .travis.yml.
Update the IRC channel URL in .travis.yml
Update .travis.yml
Add the ability to execute groovy script on the Jenkins server
Merge pull request #119 from lheinlen-os/script_text

Add the ability to execute groovy script on the Jenkins server
Bump version to 1.0.0.beta.3.
Minor typo fix.
Add credentials field in request for create_dump_slave
Merge pull request #122 from Loa/credential-field-create_dump_slave

Can't create node
Bump version to 1.0.0.beta.4
enabling the use of cookies
don't set content type in api_post_request
make exec_script use api_post_reqeust
Fix "internel" typos

Internel -> internal