replacing "from obspy.. import ..." in version.py

- this file gets used during installing obspy and can therefore not
  import from obspy
raiseifMasked decorator

- adding a decorator to raise a function/method working on Streams/Traces with masked values
- not importing Trace/Stream in decorator.py as this leads to a circular
  import
- adding it to detrend() plus very basic test
pep8
stream, waveform: Enable optional blocking of plot show
test_stream.py: Use float64 array as test stream

Using randint as source of test stream conflicts with simple casting
when multiplying with calibration constant. And consequently tests fail.
Casting / viewing array as 'float64' fixes this.
test_stream.py: test non-blocking plot
test_stream.py: Use float64 array as test stream

Using randint as source of test stream conflicts with simple casting
when multiplying with calibration constant. And consequently tests fail.
Casting / viewing array as 'float64' fixes this.
Revert "test_stream.py: test non-blocking plot"

Do not test convenience plotting functions.

This reverts commit 958563da662f0123bfa158f28b683b8c5fba9241.
Revert "test_stream.py: Use float64 array as test stream"

Leave this for own pull request.

This reverts commit 685d317501ef2779a24688a8e2361647a9550cf3.
Replacing the numpy views with true type casts.

Views do not change the underlying data and thus do not work with
custom C code that expects raw data of the correct type.
Merge pull request #501 from gauteh/plot_optional_blocking

Plot optional blocking
Merge pull request #498 from megies/raise_if_masked

tr.detrend not respecting masked arrays
Merge pull request #500 from gauteh/use_float64_for_teststream

test_stream.py: Use float64 array as test stream
pep8