Update collections.markdown

The closing square bracket on line 309 was being included in the hyperlink, rendering it invalid.
Merge pull request #502 from 7maples/patch-4

Update collections.markdown
added some updates to merchant tut
removing a mention of @order setup
Merge pull request #504 from lau03229/colms-updated-merchant

Colms updated merchant
Sync substring code example and discussion.

Substring code example has 4 uses of substring but the discussion
refers to only 3.
Merge pull request #505 from rsese/sync-substring-example

Sync substring code example and discussion.
updating info on rails -v and fixing a few minor formatting issues
updating file path to store images
First draft for today
Reworking the caching tutorial
Merge branch 'master' of github.com:JumpstartLab/curriculum
Learning jQuery RG1
Fixing reading group link
Spelling tweaks
Congres -> Congress

Fixes steveklabnik/sunlight-congress#18
<th> -> </th>

Fixes steveklabnik/sunlight-congress#19
Merge pull request #506 from lau03229/colms-second-updated-merchant

Colms second updated merchant
typo line 21

changed "complete" to "completely"
Revising outline for today