added README.rst and preprocess.py

testing the new documentation build method with a separate directory
added preprocess.py with the dynamic masking function
added includeme.rst and README.rst
some changes following docs structure
rebuilt docs
added preprocess.py and docs
shortened preprocess.py according to the changes in the dynamic_masking_of_grid.py
fixed the tab to 4 spaces in openpiv/preprocess.py
added installation example for linux in INSTALL file
added installation example for linux in INSTALL file
Merge branch 'master' of http://github.com/MathiasAubert/openpiv-python
added installation example for linux in INSTALL file
changed README to README.rst in setup.py file
added tools.imsave to save an image from an array
Merge pull request #1 from MathiasAubert/master

added installation example for linux in INSTALL
modifications to tools.py: possibility to plot vectors on image and a function to visualize the distrbution of interrogation windows
Merge pull request #2 from MathiasAubert/master

added some tools for better visualisation
added implementation of the WiDIM adaptative method
added reference
added tutorial
Merge pull request #3 from MathiasAubert/master

Implementation of the Window Displacement Iterative Multigrid (WiDIM)