Support new :refine command

This relies on a merge of
https://github.com/idris-lang/Idris-dev/pull/1083

The keybinding C-c C-r is based on Agda's default binding for refine.
Maintain a local mirror of Idris options

Also, set Idris options asynchronously. This stops the Idris menu from
locking up Emacs while Idris is busy.

Fixes #112.
Merge pull request #116 from david-christiansen/refine

Support new :refine command
Merge pull request #117 from david-christiansen/issue/112

Maintain a local mirror of Idris options
Don't give the metavar buffer focus by default

This makes it more useful as a kind of "background information".
Configuration options for metavar display

This allows users to customize more easily if metavariables should be
shown on load. Also, they can configure if the tree view should be
expanded or not by default.
Merge pull request #118 from david-christiansen/no-metavar-pop

Metavar display improvements
Read .ipkg file to get working directory

If no ipkg, default to current file's dir as before. This really helps
in getting Idris to find the imports when working on a package.
Insert bird tracks on idris-add-clause if necessary
Fix bad loading order

This fixes a problem where it was sometimes necessary to invoke
idris-mode again after loading a file before things worked.
Merge pull request #119 from david-christiansen/ipkg-load

Read .ipkg file to get working directory
Merge pull request #120 from david-christiansen/lidr

Fix .lidr support
Don't show absurdly long prompts

The new customization option idris-repl-prompt-style allows users to
pick between showing the long prompt and just having a lambda-pi prompt
with the name from Idris as a tooltip.
Merge pull request #121 from david-christiansen/ipkg-load

Don't show absurdly long prompts
Add command to go to REPL

Fixes #122.
Merge pull request #124 from david-christiansen/ipkg-load

Add command to go to REPL
Load files relative to working directory

Fixes #125.
Merge pull request #127 from david-christiansen/ipkg-load

Load files relative to working directory
Be smarter about checking file locations

Fixes #128.
Merge pull request #129 from david-christiansen/ipkg-load

Be smarter about checking file locations