Minor changes

See merge request Monash/tupak!104

- Make the limits autoset to the widest posterior
- Also fix the output filename to make more sense

- Makes a named logger "tupak" so that output only includes calls from
  tupak
- Replaces logger with logger elsewhere to effect this change
- Fixes bug where the version was printed twice

Add ability to add results together.

See merge request Monash/tupak!100

Allows pos0 to be given as a DataFrame and check if it sits outside of
the prior range.

Tests update

See merge request Monash/tupak!103

# Conflicts:
#	tupak/gw/waveform_generator.py

Adds in the ability to pass through pos0 of the walkers

See merge request Monash/tupak!102

Allow waveform_generator to not have to be initialised with the duration and sampling frequency

Closes #127

See merge request Monash/tupak!99

This allows the waveform generator to be given None for the sampling
frequency and duration (in this state, it therefore can't be used to
generate an injection). Then, when passed to the likelihood, a check if
performed to see if those attributes are set. If they are None, they are
set from the data, and if they disagree with the data, an error is raised.

Renaming variables for consistency

See merge request Monash/tupak!98

- time_duration -> duration
- fix spelling error tiime -> time
- frequencies -> frequency_array

Update cosmology

See merge request Monash/tupak!97