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.

Add functionality to strain data

See merge request Monash/tupak!94

Add Occam factor

Closes #93

See merge request Monash/tupak!86

- Removes repeated code in generating PSDs from frame files.
- Fixes a few minor bugs elsewhere

Note - this is the default for get_interferometer_with_fake_noise.., not
the default in general.

Makes the options to set the PSD methods. Retains the default behaviour
(will use aLIGO if nothing is set). But now, users must call a
`set_from_` method after initialising the PowerSpectalDensity()`.

Also adds logging messages

Previously, set_from_frame not only loaded in the time domain data, but
also applied a filter and FFT'd. This is no longer required and has
hence been removed.

- Fix error in create psd
- Fix minimum and maximum frequencies
- Improve documentation

Adds functions to set the strain data from open data, generate a PSD,
filter, and window.

- Adds a time_array and time_domain_strain to the
  InterferometerStrainData
- Adds a test for consistency between the time and frequency domain
  strain

- Adds a specific function to work out whether the frequency_array or
sampling frequency and duration where given
- General pep8 clean up
- No changes to functionality

Fixed a bug in create_time_series that produced incorrect time_arrays if a starting time other than 0 is given

Fixed a bug in create_time_series that produced incorrect time_arrays if a starting time other than 0 is given

Fixed a bug in create_time_series that produced incorrect time_arrays if a starting time other than 0 is given