Minor nuget changes

- Mark nuget package as a development dependency.
   - This comes into play when someone uses the nuget package in a project where that project itself has a nuget package. When this option is not set, then that person's nuget package includes InjectModuleInitializer, which shouldn't be the case. This is a pure "tool" nuget package, and shouldn't be distributed outside of its own nuget package.
- If ModuleInitializer.cs exists in another location, delete the template.
   - When a new version of the nuget package is available and someone updates their version, attempt to detect whether the ModuleInitializer.cs file in that project is in another location. If it is, don't create another one at the project's root.
- Get the .exe from the Release directory.
   - I noticed that you removed the `InjectModuleInitializer.exe` from the tools directory. In order to work, the nuspec file needs to know where that executable is located. This change points the nuspec file to where the executable is anyway - the project's `bin/Release` directory.
- Update license in package readme.
   - I also noticed that you changed the project's license to MIT (yay!). This change updates the nuget package's readme file to reflect this.