Fixes for `vagrant up`

vagrant:
  - check actual IP;
  - only init machine first time, just as native installations;
  - add .bash_profile to permissions fixup;
  - cleanup excessive newlines in making .bash_profile;

README:
  - include admin & debugging use;
  - info about re-initializing VM & manually running create-dev-env.sh;
  - add django admin & debug_toolbar setting info

Conflicts:
	AUTHORS
	scripts/vagrant-provisioning.sh
Merge pull request #453 from edx/yarko/vagrant-up-fix

Fixes for `vagrant up`