Restructure website

[niksirbi]

Close issue #33

This PR reorganises the website as discussed under issue #33 .

Summary of main changes

• The 3 main sections are "Data Analysis", "Programming", "Open Science"
• Each section may contain several markdown files, each corresponding to a specific long-form how to guide
• Small tips/tricks that don't warrant a long guide can go into a "Troubleshooting,md" file under the appropriate section.
• We no longer have sub-sections for specific data types. If we have have the luxury of having too many data analysis guides, we can reintroduce them.
• I've reorganised the existing content according to the above principles
• I updated the homepage, README and CONTRIBUTING accordingly
• The homepage now has cards

[adamltyson]

Looks good @niksirbi. I have a few suggestions. I know these mostly aren't part of this PR, but if we're restructuring the whole site, now seems a good time to make some decisions.

• I would remove the TOC on the main page. Eventually this will get very long and hard to navigate
• I would remove any "Coming soon" sections. These should just be added when they're ready.
• I'd reduce the toc depth on the data analysis, programming and open science pages. I find it hard to navigate, and I can't see anyone wanting to head straight for a specific subsection of a guide.
• Lastly, I'd remove the "show source" button.

[adamltyson]

I've approved, as this can be merged as is, and the other comments tackled separately if that's easier.

[niksirbi]

Looks good @niksirbi. I have a few suggestions. I know these mostly aren't part of this PR, but if we're restructuring the whole site, now seems a good time to make some decisions.

• I would remove the TOC on the main page. Eventually this will get very long and hard to navigate
• I would remove any "Coming soon" sections. These should just be added when they're ready.
• I'd reduce the toc depth on the data analysis, programming and open science pages. I find it hard to navigate, and I can't see anyone wanting to head straight for a specific subsection of a guide.
• Lastly, I'd remove the "show source" button.

Thanks for the feedback @adamltyson! I've implemented all the above suggestions in this PR.
Merging now.