Reorganizing examples, tutorial, and webpage

[skim0119]

We should rearrange where we place information that introduces pyelastica to newcomers. The problem is that we shouldn't assume people know the structure of pyelastica, especially because pyelastica is not so intuitive to native-python style. Here is the suggestion we came up with. Leave a comment if you have other ideas.

Suggestion

• example codes should be placed in an external repository, and we can make it as a submodule. We want people to install pyelastica using pip, which means the example scripts will not be exposed to users. We should expose examples (with proper description) on the website, such that it serves as a template for beginners.
• Remove binder (jupyter notebook) as a tutorial, instead clean up the tutorial on the website. Juptyer notebook can be linked at the bottom of the tutorial as run-cases. The idea is that tutorial should teach very basics of how to use pyelastica modules. Whether or not they can run the script is probably not important (and maybe cumbersome).