Fixed tags with psutil 3 new API

# memory related tags

def mem():

    """Total physical memory available on system."""

    if hasattr(psutil, 'avail_phymem') and hasattr(psutil, 'used_phymem'):

        return unicode(psutil.avail_phymem() + psutil.used_phymem())

    else:

        memory = psutil.virtual_memory()

        return unicode(memory.available + memory.used)

@ttl(5)

@refresh(10)

def memfree():

    """Available physical memory on system."""

    if hasattr(psutil, 'avail_phymem'):

        return unicode(psutil.avail_phymem())

    else:

        return unicode(psutil.virtual_memory().available)

@ttl(5)

@refresh(10)

def memused():

    """Used physical memory on system."""

    if hasattr(psutil, 'used_phymem'):

        return unicode(psutil.used_phymem())

    else:

        return unicode(psutil.virtual_memory().used)

@ttl(5)

@refresh(10)

def membuffers():

    """Buffers memory use."""

    if hasattr(psutil, 'phymem_buffers'):

        return unicode(psutil.phymem_buffers())

    else:

        return unicode(psutil.virtual_memory().buffers)

@ttl(5)

@refresh(10)

def memcache():

    """Caches memory use."""

    if hasattr(psutil, 'cached_phymem'):

        return unicode(psutil.cached_phymem())

    else:

        return unicode(psutil.virtual_memory().cached)

# disks related tags