`bcbioRNASeq()` constructor default tweak

[mjsteinbaugh]

• Set organism = NULL by default, not requiring gene annotation download from Ensembl by default. This matches the text in the F1000v2 manuscript.
• Minor documentation tweaks to some function titles.
• Unit test against stable Bioconductor release version of DEGreport.

[codecov[bot]]

Codecov Report

Merging #102 into master will not change coverage. The diff coverage is 85.71%.

@@          Coverage Diff           @@
##           master    #102   +/-   ##
======================================
  Coverage    85.8%   85.8%           
======================================
  Files          44      44           
  Lines        2254    2254           
======================================
  Hits         1934    1934           
  Misses        320     320

Impacted Files	Coverage Δ
R/methods-updateObject.R	83.1% <ø> (ø)	:arrow_up:
R/methods-extract.R	97.29% <ø> (ø)
R/methods-plotPCA.R	80% <100%> (ø)	:arrow_up:
R/AllClasses.R	83.85% <80%> (ø)	:arrow_up:

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