Add ability to query for console messages & errors

- This changes the format of console message output to use "|" as the
delimiter instead of ":"; ":" is no good for splitting when there are
URLs and error messages in the output
- WebPage tracks all console messages and clears them out on reset
Add matcher for javascript error checking
Fix spec broken in previous commit
Fixed for 1.8; removed debugging message
visit no longer tries to fix invalid URLs
Add command to retrieve URL modified by Javascript

If I use pushState to change the URL Browser#current_url still returns
the URL as it was after the original request. This commit adds a command
for RequestedUrl, which is the QtWebkit method for retrieving a URL
modified by Javascript or a redirect.
Choose platform more reliably. (Works with Jruby.)
Added note about mailing list for compilation errors.
Update documentation to point to actual capybara readme.
Recommend using "bundle exec" just in case

This avoids issues like this one: https://github.com/jnicklas/capybara/issues/585
implement "path" method for Node
add "submit" method to Node that allows to submit a form node without clicking a button
added specs for Node#path and adapted Javascript code to pass
added specs for Node#submit and fixed parameter problem
added specs for Node#path and adapted Javascript code to pass
Trigger text input events with HTML5 text-like fields: email, number, search, tel, text, and url.
Remove debugging statement
Capybara webkit doesn't listen on 8200
Bump to 0.8.0; add json as a dependency
Raise error when an invisible element receives #click so it resembles a browser more closely.