Fail to run the tests: Unable to load DLL 'SQLite.Interop.dll'

[LeiYangGH]

Hi,

This is a great project and I'm diving into it, now I want to run all the tests.

1. Open SQLite.NET.2013.sln by VS2013
2. Set test.2013 as startup project, then build this project and succeed.
3. Run in debug mode(this issue also reproduce in release mode). Then I can see the GUI with default provider and connection string, then I click Run button.
4. Soon exception thrown at TestCasesDialog.cs, line 110: {"The type initializer for 'System.Data.SQLite.SQLiteFactory' threw an exception."} {"Unable to load DLL 'SQLite.Interop.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"}