Merge pull request #4 from TomBebbington/master

Remove lots of deprecation warnings
fixed more deprecation warnings
fixed #5
Remove lock boolean flag from World and enforce configuration via WorldBuilder

Using a flag meant failing the task when misused where this API prevents
misuse at compile time.
This makes trying to access configuration methods after building the world
a compilation error because the WorldBuilder is consumed by build.
It also prevents trying to call update etc. before configuration is complete
because the World::new is made private and World are always made with
a builder.
Merge pull request #7 from jakerr/nolock

Remove lock boolean flag from World and enforce config via WorldBuilder
bumped version number
updated to latest rust and re-exported WorldBuilder to the top level of the crate
Refactored to enforce entities are always valid.

Entities must now be built and modified with EntityBuilders/EntityModifiers respectively.
These operations can also be queued, allowing systems to perform them.
Queued builds or modifications are performed at the end of the update cycle.

A `reactivated` method has been added to traits/types that need to perform operations when an entity is modified.
Otherwise, activated is only called when the entity is created, and deactivated when it is deleted.
Add `delta` argument to process in System and its related traits which
gives the time passed in seconds