Fix SignifyDeleteChanged sign setting

Closes #33.
Heavily reduce compexity by removing color options

This will be the first backwards incompatible commit for Sy for the sake
of simplicity.

For more information see:  :help signify-colors
Add showcolors.bash
Showcolors: proper cleanup
Make "jump to hunk" behave like the builtin ]c/[c

Instead of using the sign id as the primary piece of data, store
information on a per-hunk granularity.  A hunk has a start/end line as
well as a set of sign ids that have been placed within those lines.

This makes moving to the start of the next/previous hunk, as per the
behavior of the standard `]c`/`[c` bindings, pretty straight forward --
a simple filter to find relevant hunks, and then grab the first sign id.
Merge pull request 36 from @jamessan

Closes #36.
Docs: update hunk jumping
New option: g:signify_disable_by_default

You can choose to disable Sy by default now. You can enable it anytime
via :SignifyToggle (or the default mapping: <leader>gt).

Closes #34.
Bump to 1.9
Echomsg won't interpret unprintable characters
Fix wipeout error

Closes #38.
Put hl group linking into a function
Setup hl groups on VimEnter
Indicate deleted lines for ChangeDelete signs
Docs: simplify sign explanation
README: remove 2.0 note

It will be released when it's ready!
README: remove sign_change_delete var
Doc: update 'local additions' header
Docs: "amount" -> "number"
Docs: use full sentences