Disallow canonicalizing of service names

Fixes #21
Alternative of #22 

#### Advantages
1. No overhead of canonicalizing of service names
2. Better performance (not much difference)
3. Zend Framework 3 will remove canonicalizing service name feature. So, better to run away from this feature. See [this PR](https://github.com/zendframework/zf2/pull/5500)

#### Disadvantages
1. Introduces a BC break.

Note: The BC break can be avoided by create an abstract factory as a compatibility layer.