wagn installation and testing

The main goal of this PR is to be able to test mods in decks. 

Here is the new installation process:
```
wagn new mycoredeck --core-dev	# creates a new deck for testing wagn core 
                                # (asks for path to local wagn installation)
    wagn rspec					# run specs in WAGN_ROOT/spec (alias: rs)
    wagn cucumber				# run cukes in WAGN_ROOT/features (alias: cc)

wagn new mymoddeck --mod-dev	# create a deck prepared for mod testing
    wagn rspec					# run all specs in mods directory
    wagn rspec -m mymod			# run all specs for mymod (supposed to be in mods/mymod/spec)
    wagn rspec -s myset			# run spec myset_spec.rb located somewhere in mods/**/

wagn new mydeck --interactive (-i)      # guides through all installation steps 

wagn seed                      # seed production database (replaces 'rake wagn:create')
wagn seed --test-data          # seed production and test database (replaces 'env RELOAD_TEST_DATA=true rake db:test:prepare')
```
The default configuration for decks is stored in lib/wagn/config and can be overwritten or adapted in the deck's config directory.

the new all-in-one Gemfile (replaces also the wagn-dev gem)