Low-hanging bugs, unit test and code restructure

[kirsle]

This fixes some of the low-hanging bugs and also restructures the code and unit tests.

For the full details on changes, see the change log for v0.1.1, which this branch will become.

Major Changes

• API Change: Package github.com/aichaos/rivescript-go/config has been removed and instead the config.Config type can be found in the root package as rivescript.Config. To migrate existing code, make these changes:

  
  import (
    "github.com/aichaos/rivescript-go"
  -   "github.com/aichaos/rivescript-go/config"
  )
  
  func main() {
  -   bot := rivescript.New(config.Config{
  +   bot := rivescript.New(rivescript.Config{
      Debug: true,
    })
    bot.LoadDirectory("eg/brain")
  }

• API Change: the functions Reply(), SortReplies() and CurrentUser() return error objects now in addition to their old return values.

Bugs Fixed

• Fixes #1
• Fixes #15
• Fixes #16