Changed DiContainer to not install the same installer twice
Bug fix.  Was sometimes installing the same installer twice
Adjusted 'TestMultipleInstallers.cs' so that static counters are reset each time test is setup.

The 'Unity Test Tools' do not run each unit test within their own sandbox environment which means that static state is polluted at the start of each test.
Merge pull request #11 from rotorz/patch-2

Reset static counters each time test is setup.