Support l5.2 and refactor a bit

Refactor

Fixed dependencies

Fixed lazychaser#65

Fixed lazychaser#53: support l5.1.9

Fixed lazychaser#51

Merge pull request lazychaser#48 from JN-Jones/master

Laravel 5.1 support

Fixed issues with forced deletion when using SoftDeletes

Merge branch 'master' of github.com:lazychaser/laravel-nestedset

Conflicts:
	README.markdown

Added few query builder constraints