Added assembly-level ExtensionAttribute (#34)
Added assembly-level ExtensionAttribute (#34)

Adding this allows non-F# extensions to have proper visibility/interop with all CLR languages (espcially VB.NET).
This attribute is only required once per assembly, and would normally appear in `AssemblyInfo.fs`. However, here it is being placed _outside_ of AssemblyInfo.fs since that file gets automatically regenerated (and inserting it into the generated file every time is kind of a pain).
jeroldhaas/Gjallarhorn,ReedCopsey/Gjallarhorn,ReedCopsey/Gjallarhorn,jeroldhaas/Gjallarhorn