Merge pull request #80 from david-christiansen/master

Show highlighted compiler errors in Emacs
Merge pull request #81 from david-christiansen/master

Highlighting and help tooltips for notes buffer
Merge pull request #82 from david-christiansen/master

Show compiler notes tree in chronological order
Added some explanation to install

The `exec-path` bit caught me out as I normally don't use emacs. Figured it would bite more than one person, so I think it should be in the installation section.
Merge pull request #84 from joneshf/patch-1

Added some explanation to install
Add note about `idris-interpreter-path`