Changelog

set GIT_TERMINAL_PROMPT=0 when doing git clone, pull or submodule update to ensure git does not prompt for username/password in any case

change the way plugin name is expanded. It now uses the http username and password by default, like this: https://git::@github.com/. This prevents username and password prompt (and subsequently tmux install hanging) with old git versions. Fixes #7.

if the plugin is not downloaded do not source it
remove PLUGINS.md, an obsolete list of plugins
update readme with instructions about uninstalling plugins
tilde char and $HOME in TMUX_SHARED_MANAGER_PATH couldn't be used because they are just plain strings. Fixing the problem by manually expanding them.
bugfix: fragile *.tmux file globbing (@majutsushi)

update readme because of github organization change to tmux-plugins
update tests to pass
update README to suggest different first plugin
update list of plugins in the README
remove README 'about' section
move key binding to the main file. Delete key_binding.sh.
rename display_message -> echo_message
installing plugins installs just new plugins. Already installed plugins aren't updated.
add 'update plugin' binding and functionality
add test for updating a plugin

run all *.tmux plugin files as executables
fix all redirects to /dev/null
fix bug: TPM shared path is created before sync (cloning plugins from github is done)
add test suite running in Vagrant
add Tmux version check. TPM won't run if Tmux version is less than 1.9.