Addition of Help.png. Related to #225 

Created links to CREDIT and INSTALL  file in README file.

Moved authors/credits to separate file 'CREDITS'.

Documentation update 2

git are converted to pdf in pdf #232.
Using `libertine` font in pdf doc.

Added short hidden section at beginning of cookbook snippet sections explaining how to run the snippets

tweaking pehaps a listing environment for codeblock.
Related to BhallaLab/moose#225 .

* Recovered quickstart section in html, added tutorials placeholder and implemented rudimentary integration between doxygen and sphinx (dependecy on breathe sphinx extension)

* removed recursion limit change

* Added section to quickstart, and fixed a few minor typos in the install page

* Updated installation documentation with new mac osx brew install procedure. Made new section for OSX for consistency of format.

* removed some breathe related stuff from conf.py

* fixed minor typo in wildcard.py

* Recovered rdesigneur tutorial. Modified file by adding extended contents, commented out incomplete sections. Modified rdesigneur snippets page title to 'more rdesigneur examples' instead of just 'Rdesigneur'

* Added autorun statement to Compartment_net.py.

removed pyrun1.py documentation as it is exactly the same as pyrun.py.

updated vec information in quickstart to reflect actual ouput.

* uploaded fixed compartment_net.py without all my comments

* minor changes to install page, changes to doxygen readthedocs generation

* forgot to add hyperlink for doxygen page

* Added Chemical Bistables section to tutorials. Rest incoming

* Chemical Oscillators added, minor tweaks to Chemical Bistables to match Oscillators page

* Deleted extension pyc file as requested by dilawar

* Changed few names, reordered tutorials

* Changes to fix all non-references related and non-snippets related 'make html' errors

* Update crossComptNeuroMesh.py

* Added squid demo to tutorials. Removed squid demo from quickstart. Wrote a bit of theory and history about squid demo. removed redundant modules.rst file.

* Undid changes to loadSbmlmodel.py as it might have caused the mac travis to fail

Added squid demo to tutorials. Removed squid demo from quickstart. Wrote a bit of theory and history about squid demo. removed redundant modules.rst file.