Update elixir and deps versions

elixir: 0.14.2
mech: 0.8.2
Compat v0.14.2

use on_exit/2 instead of teardown
on_exit/2 in setup/2 runs after each test case
on_exit/2 in setup_all/2 runs after the test suite finished
Correct conversion functions

most of replacements are like xx_to_yy -> XX.to_yy
change url of Precompiled.zip, v0.14.2
Merge pull request #6 from Joe-noh/elixir-v0.14.2

Bump elixir's version to 0.14.2