Now uses a trigram based search. This is a lot faster and gives better
results. Closes #185.

This prevents a problem that made the local timeline very slow when
there were few posts.

Commit 5edce20302

summary:

```
*   5edce203 - (4 minutes ago) Merge branch 'master' of github.com:tootsuite/mastodon - Morgan Bazalgette (HEAD -> master, origin/master, origin/HEAD)
|\
| * 2c51bc0c - (4 hours ago)  Add missing rejection handling for Promises (#7008) - unarist (upstream/master)
| * e7a17167 - (5 hours ago) Implement the ability for an Administrator or Moderator to remove an account avatar (#6998) - Emelia Smith
| * 4fd71acc - (5 hours ago) Fix issues with sending direct messages from user profile (#6999) - Emelia Smith
| * 3f51c6ef - (5 hours ago) Weblate translations (2018-04-02) (#7007) - Yamagishi Kazutoshi
| * b04f73ce - (6 hours ago) Russian language updated (#7005) - Evgeny Petrov
| * 24611d8d - (6 hours ago) i18n: update zh-HK translation (#7004) - luzi82
| * f890d2a7 - (16 hours ago) Support all ActivityPub actor types (#6997) - Eugen Rochko
| * 33513753 - (16 hours ago) Fix unpermitted parameters warning when generating pagination URLs (#6995) - Eugen Rochko
| * 123a343d - (19 hours ago) [WIP] Enable custom emoji on account pages and in the sidebar (#6124) - David Underwood
| * f464f98f - (19 hours ago) Update Ruby to version 2.4.4 (#6964) - Yamagishi Kazutoshi
| * 6a895e1a - (20 hours ago) Fix: Prevent submission using same logic as submit button disabling. (#6993) - Emelia Smith
* | 011eda08 - (7 minutes ago) Properly cache requests using service workers - Morgan Bazalgette
* | 8dd77f17 - (5 hours ago) Fix build - Morgan Bazalgette
* | 99373236 - (19 hours ago) Add build status - Morgan Bazalgette
* | b448a3a5 - (19 hours ago) Update README - Morgan Bazalgette
* | 68fd7ee6 - (20 hours ago) Fix statuses embedded in like/boost notifs being white - Morgan Bazalgette
* | 7a9212df - (21 hours ago) Temporary workaround to only show related statuses - Morgan Bazalgette
* |   00bd10fa - (26 hours ago) Merge branch 'master' of github.com:tootsuite/mastodon - Morgan Bazalgette
|\ \
| |/
| * 993ce0e5 - (28 hours ago) improve zh-HK localization by referring zh-TW and zh-CN (#6988) - luzi82
* |   05832497 - (30 hours ago) Merge branch 'master' of github.com:tootsuite/mastodon - Morgan Bazalgette
 \ \
  |/
  * 929f58f1 - (32 hours ago) i18n: Update Polish translation (#6985) - Marcin Mikołajczak
```

with my fork of it, @ https://git.pleroma.social/howl/mastofe .

Of course you can't tell what the change is because the entire file is
written on one line, so the nearly impossible to read.

It's nice to be able to use 5000 chars from my computer and have access
to CW feature as well.

bar.

This removes the placehold.it dependency.