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