Add conda install instructions to installation.md and README.md, plus various updates to README.md

[Steph-Chong]

This PR includes various updates to the README.md:

• Removes "Using This Package" section, and instead splits the previous contents into two new sections: "Installation" and "Using scores".
• In the new "Installation" section, adds conda installation instructions.
• In the new "Using Scores" section: the existing worked example was moved into this section, and some new sentences about Jupyter Notebook tutorials were added.
• Throughout README.md, updates some capitalisation for consistency
• Throughout README.md, adds commas after "e.g." to become "e.g.," (hopefully I haven't missed any)

Because the links in the README.md also needs to work on the PyPI website, I did not use relative paths.

Also adds conda installation instructions to installation.md

@tennlee please review
@nicholasloveday if there is anything you want changed, please let me know.

[nicholasloveday]

Thanks for adding this. Particularly the conda install instructions.

[Steph-Chong]

@nicholasloveday - I made another round of changes to installation.md, partially to address offline feedback from Tennessee and partially to fix some additional bits and pieces I noticed. Would you be happy to take a look at the new changes?

[nicholasloveday]

The changes look good. A couple of small suggestions.