message: Add Intel Compiler compatibility to the Readme.
diff: @@ -34,6 +34,7 @@ For Ginkgo core library:
  * C++11 compliant compiler, one of:
  * _gcc 5.3+, 6.3+, 7.3+, 8.1+_
  * _clang 3.9+_
  + * _Intel compiler 2017+_
  * _Apple LLVM 8.0+_ (__TODO__: verify)
  The Ginkgo CUDA module has the following __additional__ requirements:
  