new options in waveform:
linestyle
grid_color
grid_linewidth
grid_linestyle

remove the linewidth in the _plotEvent

documentation in stream updated
":param data_unit:" documentation corrected
pep8 style correction in  waveform.py
Revert "pep8 style correction in  waveform.py"

This reverts commit 35a523917eb9019309c28396818c4b904042c947.
pep8 style correction in waveform.py
Option to ignore file size check in reading sac files

Checking for consistency between actual and theoretical
file size (from `npts`) can be disabled both in
`SacIO.ReadSacFile()` and in `sac.core.readSAC()`.
This is obtained by passing the parameter: `fsize=False`.

`sac.core.isSAC()` has been rewritten, in order not to
rely on `npts` to check file format, but rather checking
`nvhdr` and `delta`, as in `SacIO.IsSACfile()`.
fixes #550
Testing fsize option in reading sac files

Adds test cases for core.read() and SacIO.ReadSacFile()

See also #549
obspy-scan: plotting rectangles for gaps (instead of lines at start of gap) and new option --print-gaps
minor change to previous commit
fixes #553
fixing a bug introduced in 4e70c059e8f76d3e71da45d31ac31b6759f7b4b2

(IndexError in case of a gapless seed id)
fixes #554
Merge pull request #555 from obspy/554

fixes #554
removing a outdated comment
Making isSAC() more robust
signal: extend coincidence trigger

 - now has possibility to use event template waveforms
 - event triggers that excceed similarity levels get included in results
   even when network coincidence sum is not met
 - tutorial example
 - test, simple doctest for helper routine in cross_correlation
 - changelog
Added `lovrok` to required sac header fields
missing changelog entry for 4e70c059e8f76d3e71da45d31ac31b6759f7b4b2
Some modifications in isSAC()

- nvhdr >=1 (normally it is always 6).
  This avoids validating as sac files those files which
  have a lot of zeros at the beginning.
- lpspol, lovrok and lcalda are allowed to be undefined
  (though this is not good practice for a sac file...)
backwards compatibility for testing