Remove more Option[_] from result

This PR supersedes my previous PRs. (#1, #2)

### Major changes
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#### Removed more `Option[_]` from results
- Especially around `List` or `Map`.

#### Updated SBT library dependencies to the latest
- SBT 0.12.4, Scala 2.10.2, Akka 2.2.0, etc.
- Scalatest is updated to the latest snapshot for `scala.concurrent.Future` support. ([memo](https://github.com/guersam/scala-redis-nb/commit/626e197e9983ba9285283ad142ca27adbc6aee90#commitcomment-3631484))

#### Ported major test cases from previous repo
- Test cases for _Key_, _Hash_, _Set_, _SortedSet_ are converted.
- Added `trait RedisSpecBase` for commonly used components.

#### Several fixes
- Most major commands work as expected.