Update less peerDependency to 2.1
Update less-loader to work with less 2.x

Now the less-loader uses a less-plugin to add a WebpackFileManager. This file
manager is now responsible for webpack's special resolving logic. Since less 1.x
doesn't have a plugin api this change is incompatible with less 1.x.
Add note on isSync-check
Work around double callbacks on less errors

#28
Add bootstrap as sufficient complex and popular example
Remove unused node_modules folder
Fix error where node_modules were not correctly resolved
Add test for node_modules
Merge pull request #28 from webpack/fix/less-2

Add less 2.x support