Convert numerical dtypes from strings to real types.

This only covers the simple numerical types. That is, types that have an
explicit byte order are unchanged for the moment. String types are also
unchanged.

See #823.
Merge branch 'master' into dtype-compatibility
Convert numerical dtype strings in np.fromstring.
Remove unnecessary np.dtype() calls.

Doing stuff like np.dtype(np.float32).type just returns np.float32, so
we can simplify that a little bit.
Use native_str() for dtype setting.
Fix types in obspy-mopad gmt command.

Apparently, NumPy want io.BytesIO, whether on 2.x or 3.x, so this is
pretty easy to fix.
Add native_str to MSEED record script.
Use native_str on dtypes with explicit byteorder.
Convert a few more remaning string dtypes.
Make createEmptyDataChunk handle string dtypes.
Fix writeSLIST with NumPy 1.4.

The delimiter needs to be a bytestring, so that it doesn't change the
final string to be written to the (opened as bytes) file.
Fix writeTSPAIR with NumPy 1.4.

It seems np.savetxt is not too smart about writing to bytestream files.
And it appears that converting the UTCDateTime to a string creates a
Unicode string, which savetxt does not encode. Anyway, dropping the
np.savetxt call seems like it would be faster, since we don't need to
iterate through the data a couple extra times.
Use np.ascontiguousarray where needed.

This fixes a KeyError with NumPy 1.4, since it expects a regular string,
instead of a Unicode string when specifying flags to np.require.
Better np.frombuffer compatibility with NumPy 1.4

NumPy 1.4's frombuffer does not like empty buffers.
Fix np.savetxt call in WriteSacXY.

Again, delimiter needs to be a bytestring.
Use np.dot instead of np.matrix.dot.

The class shortcut doesn't appear to be available in NumPy 1.4.
Don't use np.testing.assert_allclose.

It's not available in NumPy 1.4.
fix map plots on centos6 (old mpl version, no path effects)

will make some image tests fail on centos6 (but who cares ;))
fix previous commit
Make core.compatibility.frombuffer accept strings.