use local JQuery

Using the CDN one makes developing over slow wi-fi really tedious.  I
know there's a good reason to use the CDN one, so maybe I'm too cranky.
Happy to revert is someone feels strongly.
Overhaul of much of the copy.

the PR will have more details, but generally:

Small Things:

* fix typos
* improve wording/flow in places
* update tech stuff with our current state of the art

Bigger Things:

* Remove "senior" from rails job, as that is now no longer a restriction
* Remove some hyperbolic language
* Be more explicit about how we as a team want to learn just as much as we expect it of candidates.
* Remove stuff about GitHub and side projects, as this isn't a factor for us.  Instead, replace with "love of craft" which is more in line with what we look for.
* Probably some other stuff I'm forgetting that I'll remember when I see the diff
typo
reword code review slightly
s/3/several
remove some version for stuff about monthly gem updates
try to be more amusing :)
s/things/ideas
will never refuse the use of an emdash
Merge remote-tracking branch 'origin/master' into tighten-up-job-descriptions

Conflicts:
	_includes/_engineering_jobs.html
	jobs/lead-full-stack-rails.html
Merge remote-tracking branch 'origin/tighten-up-job-descriptions' into tighten-up-job-descriptions
Merge pull request #43 from stitchfix/tighten-up-job-descriptions

Refresh a lot of the copy