Replacing GPL spline code by LGPL spline code

Now using the LGPL SPLINE library
http://people.sc.fsu.edu/~jburkardt/c_src/spline/spline.html

Adding an extra test, as the current obspy tests do not seem
to cover the interpolation part.

See #827.
pep8
typos and py3k
Trigger length of 1 sample (on==off) resulted in empty array.
Replaced if else with try Except to avoid unnecessary if checks.
x axis inputs must be strictly increasing

thx to @QuLogic for pointing that out
std of single value is always 0
beautifying
Add test for infinite loop mseed files.
mseed: Make Python parser resilient to invalid files.

It suffers from the same infinite loop bug as libmseed.
Merge pull request #893 from syngron/pr_trigger_empty_array

Trigger length of 1 sample (on==off) resulted in empty array.
add SACPZ write support for Inventory (tested against one station served by IRIS SACPZ WS)
changelog
clarification for DIP header comment in SACPZ output
Response.get_paz() returns deepcopy now, much safer

additional minor fixes
Change print statements to functions in comments.
mseed-recordanalyzer: Fix incorrect indent.

Printing only worked when the file was big endian.
Merge pull request #879 from megies/write_sacpz

add SACPZ write support for Inventory
Fix build errors.

One missed print statement and one minor flake8 warning.
Remove unnecessary plt.gca() calls.