Updated CONTRIBUTORS
libbladeRF: Renamed enum to differentiate between struct of same name

Non-functional, cosmetic-only change.
Fixed for bugs found via Coverity
Merge pull request #122 from litghost/coverity_fixes

Fixes for bugs found via Coverity
cli: FPGA's don't exist on unopened devices.
Fix warning that caused CMake to determine the version of libusb

A recent flag change has made the compiler treat warning as errors, this caused
the implicit declaration of printf to caused ver.c to not compile. This in turn
made CMake believe that it couldn't even find the API VERSION macro.
Windows: Call Sleep() with a value > 0.

From the documentation:

"A value of zero causes the thread to relinquish the remainder of its
time slice to any other thread of equal priority that is ready to run.
If there are no other threads of equal priority ready to run, the
function returns immediately, and the thread continues execution."

Thanks Simon!
Update cmake_minimum_required to 2.8.3 for host/

Resolves issue #123

host/CMakeLists.txt uses CMAKE_CURRENT_LIST_DIR, which does not exist
before 2.8.3.  Updating this to avoid obscure build errors on old
machines.

Also adding a few missing cmake_minimum_required directives to avoid
a warning that likes to pop up when they're missing.
Add README note about minimum cmake version
Merge pull request #124 from rtucker/issue123_cmake_version

Bump cmake_minimum_required to appropriate value.