Updated RTD and removed old examples

Updated online documentation. Changes include:

Split installation instructions out to a new section in the sidebar
Moved the "quick guide" inside the User's guide
Added a separate "Downloading EIS Data" section with an example for the new Fido client
Added an "Code Examples" section that contains copies of most useful examples for easier reference
Added a "Community Guidelines" section

Assorted other updates:

Added MPFIT license file
Updated README.md
Removed all remaining main examples (they are already included in the online docs)
Disabled testing the Fido client due to NRL server maintenance

Note: there are NO code changes in this PR. Therefore the version number will not be incremented.

Addresses issues #3, #21, #22, #52, #60, & #64. These issues will be closed properly once the RTD hosted docs are updated (hopefully soon).

USNavalResearchLaboratory / eispac