Tutorial Day 1 review

[martinberoiz]

From a review:

• In Day 1, Tutorial 2, the import gwpy command takes a very long time, presumably because of "Matplotlib is building the font cache; this may take a moment". It would be good to have a comment for this step noting that it takes some time to initialize. DONE (see Remove pylab #35)
• In Day 1, Tutorial 3, the Q-Scan challenge would benefit from motivating why the time range should be much smaller, i.e., this event was for a binary black hole.
• In Day 1, Tutorial 4, Exercise 1.4.3, I would recommend providing a waveform, I used and suggest IMRPhenomPv2 successfully (IMRPhenomPv2_NRTidal worked for me also). The reason for this is that the waveform on the event page with the parameters (the student is pointed to) is based on a combined samples from different priors and does not map to one of the LAL waveforms listed in this tutorial.

[duboism]

Part of this were fixed in #35.