Add virtual destructor
Add travis-ci yml file
Let the image loader return the actual image pointer instead of having the data be constructed
Override LoadImage for ktx files
Add some static casts
Relax the test parameters on eigenvalue calculation
Make unit tests a bit more deterministic
Fix a bunch of MSVC compiler warnings and errors.

Most notably, we need to actually fix a bug in MSVC that doesn't know how to properly instantiate
enums in partial template specialization. There are more details outlined here:

http://stackoverflow.com/questions/15466594/why-does-msvc-fail-to-compile-this-template-function

The fix in this commit closes #10

Also in this commit is a hacky way to allow GL defines. Apparently "LoadImage" is defined as a
macro even with WIN32_LEAN_AND_MEAN. This means that we have to #undef the code that includes
it, meaning that we also need to make sure not to actually mix GLDefines.h with any file that needs
to use the functions from Windows.h