deprecate get_core_count, update vsc.utils (+ update develop)

**WARNING**: this seems to break OS X functionality, so be careful when merging this in...

```
ERROR: test_easyblock (test.framework.easyblock.EasyBlockTest)
make sure easyconfigs defining extensions work
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test/framework/easyblock.py", line 84, in test_easyblock
    self.assertRaises(NotImplementedError, eb.run_all_steps, True, False)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/unittest/case.py", line 456, in assertRaises
    callableObj(*args, **kwargs)
  File "easybuild/framework/easyblock.py", line 1759, in run_all_steps
    self.run_step(stop_name, step_methods, skippable=skippable)
  File "easybuild/framework/easyblock.py", line 1642, in run_step
    m(self)
  File "easybuild/framework/easyblock.py", line 1699, in <lambda>
    ('fetch', 'fetching files', [lambda x: x.fetch_step()], False),
  File "easybuild/framework/easyblock.py", line 1162, in fetch_step
    self.set_parallelism()
  File "easybuild/framework/easyblock.py", line 1043, in set_parallelism
    nr = get_avail_core_count()
  File "easybuild/tools/systemtools.py", line 61, in get_avail_core_count
    num_cores = sum(sched_getaffinity().cpus)
  File "/Users/kehoste/.local/lib/python2.7/site-packages/easybuild_framework-1.8.0dev-py2.7.egg/vsc/utils/affinity.py", line 205, in sched_getaffinity
    ec = _libc.sched_getaffinity(pid_t(pid),
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 366, in __getattr__
    func = self.__getitem__(name)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 371, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(0x7fff644211e0, sched_getaffinity): symbol not found

======================================================================
ERROR: test_core_count (test.framework.systemtools.SystemToolsTest)
Test getting core count.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test/framework/systemtools.py", line 43, in test_core_count
    core_count = get_core_count()
  File "easybuild/tools/systemtools.py", line 72, in get_core_count
    return get_avail_core_count()
  File "easybuild/tools/systemtools.py", line 61, in get_avail_core_count
    num_cores = sum(sched_getaffinity().cpus)
  File "/Users/kehoste/.local/lib/python2.7/site-packages/easybuild_framework-1.8.0dev-py2.7.egg/vsc/utils/affinity.py", line 205, in sched_getaffinity
    ec = _libc.sched_getaffinity(pid_t(pid),
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 366, in __getattr__
    func = self.__getitem__(name)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 371, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(0x7fff644211e0, sched_getaffinity): symbol not found

```