Update composer.json

Add branch alias
Merge pull request #209 from nkt/patch-1

Update composer.json
Adding 'doubleval' and 'intval' optimizers, ignore constant propation of constants containing 'VERSION'
Merge branch 'master' of https://github.com/phalcon/zephir
Adding 'prepare_virtual_path' and 'basename' optimizers, using read only parameters as indexes in multi-index array update
Adding 'filemtime' optimizer
Optimizing 'instanceof' operator by prefetching class entries
Removing extern modifiers
Fixing passing stack parameters to internal methods, reseting refcount to static variables
Fixing passing stack parameters to internal methods, reseting refcount to static variables (2)