[Feature]: Add alignment and cigar getters

[MillironX]

Closes #39

Types of changes

This PR implements the following changes:

• ✨ New feature (A non-breaking change which adds functionality).
• 🐛 Bug fix (A non-breaking change, which fixes an issue).
• 💥 Breaking change (fix or feature that would cause existing functionality to change).

📋 Additional detail

Add methods to BioAlignments.alignment and BioAlignments.cigar to pull a PairwiseAlignment and CIGAR string from a Haplotype, respectively.

See the updated docs for runnable examples.

☑️ Checklist

• 🎨 The changes implemented is consistent with the julia style guide.
• 📘 I have updated and added relevant docstrings, in a manner consistent with the documentation styleguide.
• 📘 I have added or updated relevant user and developer manuals/documentation in docs/src/.
• 🆗 There are unit tests that cover the code changes I have made.
• 🆗 The unit tests cover my code changes AND they pass.
• 📝 I have added an entry to the [UNRELEASED] section of the manually curated CHANGELOG.md file for this repository.
• 🆗 All changes should be compatible with the latest stable version of Julia.
• 💭 I have commented liberally for any complex pieces of internal code.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +3.53 🎉

Comparison is base (0116518) 86.52% compared to head (373e485) 90.06%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #42      +/-   ##
==========================================
+ Coverage   86.52%   90.06%   +3.53%     
==========================================
  Files           7        7              
  Lines         282      312      +30     
==========================================
+ Hits          244      281      +37     
+ Misses         38       31       -7     

Flag	Coverage Δ
unittests	90.06% <100.00%> (+3.53%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/SequenceVariation.jl	100.00% <ø> (ø)
src/Haplotype.jl	93.33% <100.00%> (+0.89%)	⬆️
src/Variation.jl	86.86% <100.00%> (+3.33%)	⬆️

... and 1 file with indirect coverage changes

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