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

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