Add SONAME. Fixes #65.
example: replace arial with a free font

Arial is a proprietary font and cannot be included in another package in
distributions like Debian. Replaced it with Liberation.
example: fix compilation command
add CMAKE_INSTALL_LIBDIR

Keeps the default to 'lib', while allowing to use it like so:

-DCMAKE_INSTALL_LIBDIR=lib/x86_64-linux-gnu
Merge pull request #70 from jpleau/libdir

add CMAKE_INSTALL_LIBDIR
Merge pull request #69 from jpleau/examples

example: typo in compilation command, replace arial with a free font
Don't use dereference operator in events example
Merge pull request #72 from eco/patch-1

Don't use dereference operator in events example
Added CMake Find_Package script and debug suffix

* This allows easy inclusion of EntityX in CMake projects using
`Find_Package(EntityX)`.
* Also debug versions now use the `-d` suffix, no longer overwriting
release builds (e.g. `entityx-d.lib` rather than `entityx.lib`).
Merge pull request #73 from MarioLiebisch/cmake-additions

Added CMake Find_Package script and debug suffix
Add Non-Templated SystemManager::update() Method

- Added a non-templated updateAll() method to the SystemManager that
updates all systems in the manager.
- Adds a test for updateAll().
Rename SystemManager::update_all() and Add Documentation

- Renamed SystemManager::updateAll() to SystemManager::update_all() to
make it consistent with the existing naming convention.
- Added documentation for SystemManager::update_all().
Merge pull request #76 from excaliburHisSheath/master

Add SystemManager::update_all() Method
CMake fix for AppleClang.
Remove event and "system" subsystems.

Documentation needs to be updated.

Events are replaced with callbacks on EventManager:
on_entity_{created,destroyed} and on_component_{added,removed}.

Discussion on events in #71.