Remove redundant paragraph

[92amartins]

Closes #73 and #77

[92amartins]

I think that the wercker build fails because there's no tapwater dataset in branch statsr@BayesFactor from which it pulls code during environment setup. I see some possible solutions for this:

1. Point wercker to statsr@master
2. Rebase statsr@BayesFactor to the master branch
3. Include tapwater dataset in the BayesFactor branch

Don't have enough background on the project to make a call.

Quitting from lines 203-238 (04-normalgamma-01-inference.Rmd) 
Error in bayes_inference(tthm, data = tapwater, prior = "NG", mu_0 = m_0,  : 
  unused arguments (prior = "NG", mu_0 = m_0, s_0 = sqrt(s2_0), v_0 = v_0, method = "theoretical")
Calls: local ... handle -> withCallingHandlers -> withVisible -> eval -> eval
In addition: Warning message:
In data(tapwater) : data set 'tapwater' not found
Execution halted
Error in Rscript_render(f, render_args, render_meta, add1, add2) : 
  Failed to compile 04-normalgamma-01-inference.Rmd
Calls: <Anonymous> -> render_new_session -> Rscript_render
Execution halted

[mine-cetinkaya-rundel]

I'll close this since it seems like it got taken care of in another PR.