Keep consistency with deployer executable naming

[bpolaszek]

Q	A
Bug fix?	No
New feature?	No
BC breaks?	No
Deprecations?	No
Fixed tickets	N/A

This minor change guesses the local name of the deployed.phar script (or ./vendor/bin/dep) for using in console output.

Example with a locked deployment:

$ dep deploy 

Deploy locked.                                        
  Execute "dep deploy:unlock dev" to unlock.

$ ./vendor/bin/dep deploy 

Deploy locked.                                        
  Execute "./vendor/bin/dep deploy:unlock dev" to unlock.

$ php vendor/bin/dep deploy 

Deploy locked.                                        
  Execute "php vendor/bin/dep deploy:unlock dev" to unlock.

$ php deployer.phar deploy 

Deploy locked.                                        
  Execute "php deployer.phar deploy:unlock dev" to unlock.

$ ./bin/deployer deploy 

Deploy locked.                                        
  Execute "./bin/deployer deploy:unlock dev" to unlock.

If called script is found in PATH, a basename() is applied to avoid showing full path (like /usr/local/bin/php or /home/user/.composer/vendor/bin/dep, for instance).
This will help people unfamiliar with the tool to just copy/paste suggestions.