and time marg before moving onto dist and tiem nad phase marg

- Add doc file on CBC PE
- Add introduction text

ratio looks a bit off: need to figuring out what's going on with the
normalization

Allows easier access to the Likelihood, GWT, WaveformGenerator, and
run_sampler

- Fixes bug when setting truths
- Remove mu=None, sigma=None in hyper PE example

- Adds a tests flag for which the sampler only runs 100 steps
- Set the samples as random samples to test plotting
- Fix problems in a few of the examples

changed random seed to avoid multi-modal posteriors.  Added comments to tutorial so user can understand each step

Closes #68 by giving a simple interface to set the log-level (unless set
at the script level) and whether or not to use cached data.

Revert "Revert "Moritz Huebner: Removed default parameters for sampling frequency and time duration in the waveform generator""

This reverts commit 91e90f0d.

Revert "Moritz Huebner: Removed default parameters for sampling frequency and time duration in the waveform generator"

This reverts commit e4ac1430.