switched links to Seeed except DIY, GPRS, and GPS

[Frijol]

fixes #33

• Change all links to module purchases over to Seeed
• Take down our shop (moved to Take down shop.tessel.io #36)
• Make any /shop references redirect to Seeed Tessel shop

[Frijol]

Seeed is missing:

• DIY module
• GPS module

If you click on those links in our modules section, they'll go to the Tessel store, so I didn't shut down the Tessel store in this PR.

@johnnyman727 what do you want to do about those links?

[johnnyman727]

@Frijol we should just remove them for now until Seeed gets them up. I'll email them about it.

[johnnyman727]

Looks good but can we put "temporarily unavailable" and disable the "Buy" button for the GPS and DIY modules?

[Frijol]

made #35 so we don't forget to fix those when they come online

[Frijol]

@HarleyKwyn I don't actually know how to take down our shop, but we should make shop.tessel.io redirect to tessel.io/shop (which as of this PR redirects to Seeed's Tessel page). Can you help?

[Frijol]

Moved that problem to #36 so we can merge this now

[johnnyman727]

lgtm