ignore strand when showing annotation tracks

[kevinrue]

When the genomic range that defines the visible region= is stranded, annoTracks that are antisense to region are not visible.
This PR offers to make them visible.

Thanks!

[codecov-io]

Codecov Report

Merging #69 into master will decrease coverage by 3.11%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #69      +/-   ##
==========================================
- Coverage   29.85%   26.74%   -3.12%     
==========================================
  Files          21       21              
  Lines        2629     2382     -247     
==========================================
- Hits          785      637     -148     
+ Misses       1844     1745      -99

Impacted Files	Coverage Δ
R/plotting.R	0% <0%> (ø)	⬆️
R/BSseq_class.R	61.58% <0%> (-9.71%)	⬇️
R/hdf5_utils.R	69.23% <0%> (-9.56%)	⬇️
R/BSmooth.R	66.16% <0%> (-9.02%)	⬇️
R/permutations.R	47.42% <0%> (-6.04%)	⬇️
R/BSseq_utils.R	32.25% <0%> (-5.58%)	⬇️
R/combine.R	84.43% <0%> (-2.38%)	⬇️
R/read.bismark.R	87.77% <0%> (-1.44%)	⬇️
R/combine_utils.R	97.61% <0%> (-0.39%)	⬇️
... and 10 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2cfeed6...c0258d0. Read the comment docs.