Corrected typo in the basics of PE page, maths section. The parenthesis containing the squared exponent should read (y_i - (t_i * m + c)) instead of (y_i - (t_i * x + c)) for a model H defined by y = m*x + c.

This updates to an anaconda python image and removes redundant tests
rerunning examples so that the tests finish in a more reasonable amount
of time. Many requirements are also moves to an
optional_requirements.txt file.

- Adds in comments from Denyz, and general tidy up.
- Closes #83

- Moves the hyperPE likelihood to core
- Adds the GaussianLikelihood
- Update docs
- Update examples

- Convert markdown readme to rst
- Add pip install entry to installation instructions

- Move instructions to docs
- Update and simplify readme
- Add note on HTTPS