Fix libdawg linking error on Windows

[zmertens]

Currently, when building on Windows 10 using Visual Studio 2015 Community (64bit), there is a
LNK1181: cannot open input file "libdawg2.lib" error at the end of the build process for project "unittest_Dawg_parse_test". The issue may be caused from trying to link "libdawg2" to a unit test target in the dawg/tests/Unit/CMakeLists.txt file. This issue appears to be isolated to Windows systems and is minor.

Possible solution:

• Modify libdawg2 library to link correctly, possibly need to use {CMAKE_STATIC/SHARED_LIBRARY_SUFFIX/PREFIX}

[zmertens]

So all I needed to do was change libdawg to libdawg-static