Handle changing a dep from git to hex

Closes #36.
Update hex_web
Return dep tuples to elixir

Fixes an issues where mix does not know if the dependency is optional
after the optmization to not read mix.exs.
Umbrella projects are not supported

Closes #37.
Show if dependency is optional when publishing

CLoses #38.
Reword tarball fetch output to show we use cached copies

Closes #29.