PPSD: enable getting/plotting mode and mean psd values
Merge branch 'master' into ppsd_stats
minor refactoring
minor docstring refactoring
Add ZMAP write support for earthquake catalogs
Improve python 3 compatibility

...by explicitly encoding/decoding strings when writing/reading to files.
Fix minor issues
Open files in context, minor improvements
Minor improvements
Add ZMAP read support
Remove unused doctests
Move ZMAP support do dedicated package
Fix python 2.6 compatibility
Another python 2.6 compatibility fix
Rename zmap module to core, fix doctests
Fix python 3.3 compatibility issue
Added obspy.zmap to doc overview page.
Some restructuring of the zmap documentation.

Fixed some RST issues and reordered it a bit. Also included the
licensing information.
Allow zmap to read from a string
Fix whitespace (PEP8)