Fix #2627 (source maps with a PATH_PREFIX)

When you set ROOT_URL_PATH_PREFIX, source maps are not found because the server serves them at a different path from where the client looks for them.

I don’t understand this code super well, but based on what’s reported in issue #2627, the new code seems strictly more correct than the old code.
api doc: add a working showdown (Markdown) example

I couldn't figure out an easy way to include a Spacebars operator like
{{#markdown}} in a Markdown code block, hence the <code>{&#123;#...
trickery. I think I can clean this up a little with the {{dstache}}
template helper, though. See next commit.
api doc: use {{dstache}} template helper

Less/cleaner source code.
Merge branch 'pr-2673-merge' into devel
fix typo (use of & vs. &&)
Template.created has now more use.
Merge branch 'pr-2681' into devel
Missing a period(.) in this one sentence

Entire document has sentences ending in periods except for this one
(including the ones ending in quotes).
add --test flag to Meteor CLI for velociy CI support

- establish a DDP connection to Meteor
- subscribe to test results
- hit running web server
- exit with appropriate status code after tests have completed
clean up velocity --test pull request

- remove hardcoded localhost:3000
- add documentation to command
- remove emoji
Export same-origin check and `end_of_redirect_response` template.

Export some properties to allow developers to override them to
support logging in using the OAuth redirect flow from cross origin
domain.
Remove 'reload' timeout.

This timeout was designed for a very specific case (hit stop during a
hot code push, come back to the page later and you don't expect your
session state to still be there), but it's not clear what length of time
is right for that, nor whether it's even what users expect (and if there
should be a timeout, it probably varies from package to package
depending on what type of data the package is storing in sessionStorage
-- e.g. for OAuth logins, 30 seconds is way too short of a timeout).

Fixes #2696.
Move velocity code to a separate file for easier maintenance.
Mark run --test as experimental.
comments
code style cleanups to match style guide.
help text nitpicking.
Merge branch 'pr-2680' into devel
Merge branch 'devel' into release-0.9.4

Conflicts:
	tools/help.txt
Fix whitespace