Speeding up triggerOnset with deque

- will bring a big speed up, when the trigger list is very longish
- proposed by
  http://pyvideo.org/video/1780/transforming-code-into-beautiful-idiomatic-pytho
Being more pythonic, refactoring

- using else statements in for loops
- proposed by
  http://pyvideo.org/video/1780/transforming-code-into-beautiful-idiomatic-pytho
add option "prefix" (default "obspy-") for NamedTemporaryFile
Merge pull request #546 from megies/tempfile_prefix

"obspy-" prefix for temp files