fixes #133
inserted tests for fix for #133
Merge pull request #134 from wkerzendorf/plasma/test_high_temperature

Test high temperature - outside of interpolation range of zeta factor
Update CHANGELOG.rst
added geogebra files describing the distances to inner and outer boundary
added sphinxcontrib-tikz to the requirements
inserting documentation about the geometry
changed the geogebra files
added png files for documentation