Add 2D elasticity notebook example

Address issue #68

Add first draft of elasticity notebook. Still need to work on the api for random microstructures for elasticity for more than 2 phases. Need to know what units Sfepy expects the Young's modulus to have.
Add HTML titles, logos and icons.

Address #52.

The colors for the logo are #58b91a and #f1d71d
Merge branch 'master' into elasticity-notebook
Add re-sized coefficients to 2D elasticity notebook

Address issue #68

Add re-sized coefficients to 2D elasticity notebook to demonstrate how
to use the method resize_coeff.
Switch to Bootstrap theme

Address #52

Bootstap theme seems much nicer.

 * remove search box

 * switch to sphinx_bootstrap theme

 * using contents file instead of index

 * reduced size of logo

 * remove copyright
Add MKS equation derivation

Address issue #65

Add MKS equation derivation to show where the MKS equation comes from.
Move master file back to index.rst

Address #52

PyMKS icon can't point at anything other than the master file. Include
the introductory notebook in the master file.
Clean up README.md for webpages.

Address #52

Clean up from page by merging README and IPython notebook in
index.rst.
Correct typos in the MKS derivation.

Address issue #65

Correct typos in the MKS derivation
Clean up intro for front page

Address #52
Merge branch 'elasticity-notebook'

Fix #68, fix #65
Merge branch 'master' into issue52-docs
Renname notebooks to have shorter names

Address #52
Clean up docs for front page

Address #52

 * Fix casting warning in FE model.

 * Create functions to render images for front page.
Add equation to derivation
Merge branch 'elasticity-notebook'
Merge branch 'master' into issue52-docs
Add image for intro notebook.
Switch to Mathjax from PNG images

Address #52

Using Mathjax will take much less space in the repository.
Clean up the installation instructions.

Address #52

 * Other small improvements

 * Removed half finished examples from examples contents

 * Add theory section