Handle error messages caused by missing binary libraries.
Improves sudo propmt
Use RUBYLIB instead of RUBYOPT to add the bundle lib path to ruby $LOAD_PATH.

This allows `bundle exec` to be run when the bundler gem is at a path that includes spaces (which is pretty common in windows environments).
added documentation on how to set up Bundler for Development
updated the How to set up bundler for development
updates to Bundler for Development
deleted white spaces ?
white space gone
Merge pull request #2558 from jendiamond/bundlerfordev_doc

Added documentation on how to set up Bundler for development
expand contribute, mention alias
Load current_ruby from shared_helpers.rb

In case of commands run via bundle exec, we do not require all of
bundler in that environment and we only require bundler/setup there.
Which creates problems because Bundler is unable to find current_ruby therej
Raise user friendly errors in case of Cyclic Dependency

Fixes #2506
Merge pull request #2562 from bundler/fix-current-ruby-for-exec

Load current_ruby from shared_helpers.rb
Changed cyclic dependency error message

Also change raise code to be inline with current
convention.
Extract error message from TSort::Cyclic and print

Also updated test case to include check on error message
Remove unnecessary quotes around bundler lib path. 

As suggested by gnufied.
Improve RUBYLIB example in exec spec.
Extract the mutually dependent gems from error message

On MRI and Ruby 1.9 error message pattern looks very
different from what we see on JRuby and other versions of
Ruby.
Merge pull request #2536 from equinux/master

Use RUBYLIB instead of RUBYOPT to add bundle lib path to ruby $LOAD_PATH.
Use http:// instead of git:// on GitHub URL's