Allow users to press enter in autocomplete by default. Close #1296

Not being able to press enter in all contexts by default (including autocompletion) is surprising.
Users can still select a completion with tab.
Mention license in readme, close #973
Adjust contributing wording to avoid any misleading wording, close #1614
Fixed couple of compile-time warnings #1658
Fixed couple of compile warnings
Fixed couple of compile-time warnings #1658
Bring back some functions, that might broke inner API
Encourage users to go the mailing list for questions

A number of issues I've addressed in the past weeks were questions that had a better
chance being answered in the mailing list than being a github issue.
Most recently #1704. Also added a section on what to include on bug reports.
Fix remaining warnings that can be fixed

Outstanding warning is caused by fetch. Did end up removing populate
as it referred to a nonexistant function and couldn't have worked since
it was imported
Fix inline-exception warning properly
Merge branch 'pr/1698'
linux_deps.sh: If 'which curl' fails, exit with its return code.
linux_deps.sh: re-use downloaded LightTableLinux*.gz, clojure-plugin

* download LightTableLinux*.tar.gz only if it doesn't exist and always
  verify its sha1 checksum.
* store clojure-plugin as a git-submodule and clone it only once. Then
  update it with git pull --rebase
linux_deps.sh: buildVer=0.6.7