Fix cvxopt recipe for OS X

@asmeurer The atlas package is actually unnecessary for OS X, as LAPACK and BLAS are packaged with the OS. Here's the ldd-equivalent output:

```
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/amd.so:
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/base.so:
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib (compatibility version 1.0.0, current version 1.0.0)
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/blas.so:
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/cholmod.so:
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib (compatibility version 1.0.0, current version 1.0.0)
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/lapack.so:
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib (compatibility version 1.0.0, current version 1.0.0)
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/misc_solvers.so:
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib (compatibility version 1.0.0, current version 1.0.0)
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
/Users/chris/anaconda/lib/python2.7/site-packages/cvxopt/umfpack.so:
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib (compatibility version 1.0.0, current version 1.0.0)
	/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1213.0.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 283.0.0)
```

Also, I realize this isn't the repo backing the anaconda builds - but I'd like to get this fixed in the official channel, so please let me know if you happen to know who the appropriate person to contact is.