New helper function.

Added a new helper function converting a vector of unit length given in
dip and azimuth to a unit vector in the vertical, south, east coordinate
system.
Added arbitrary dip/azimuth rotation.

Added a new function that allows to specify the orientation of each
component seperately with dip and azimuth. The components do not have to
be orthogonal to each other it should work nonetheless. The output are
three new arrays, always oriented Up, North, East
Added rotate2ZNE method to obspy.xseed.parser.Parser

This enable the (very basic) fully automatic rotation of arbitrarily
oriented components to ZNE. Also renames the channels.
Added test for the Parser rotation method.
Added test files.
Updating changelog
Better docstrings.
Merge branch 'master' into rotations.

Resolved conflicting CHANGELOG.
Merge branch 'master' into rotations

Conflicts:
	CHANGELOG.txt
	obspy/signal/rotate.py
	obspy/xseed/parser.py
resolving conflicts
pep8
Merge pull request #569 from krischer/rotations

Rotation of non-standard orientations to ZNE