Clear redisx package.

The features were moved to the main package long ago.
Update doc to say that NewPool is deprecated.

I hope that the new doc will discourage people from forking the project
to add arguments to NewPool.
Add test for EXEC errors.
Fix connection pending count.

To handle the case where Receive is called before Send, decrement the
pending count after the reply is read.

Fixes #78
Rename pooled connection receiver.
Improve pooled connection concurrency support.

Add support for one concurrent reader and one concurrent writer on
pooled connections.

Fixes #73
Rename pool test functions.
Improve Pool.Dial doc.
Fix code formatting.
Fix typo in doc.
Update commandinfo.go

Run `gofmt -s -w .` on the repo.
Merge pull request #82 from creack/patch-1

Update commandinfo.go
Add concurrency benchmarks

Use pool (multiple connections) and textproto.Pipeline (single
connection) to issue commands concurrently.
Add note about concurrency to error messages.
Improve concurrency doc.
Use internal package.

Move function lookupCommadInfo in redis package to LookupCommandInfo in
new internal package.

Move test only function DialTestDB function in redis package to Dial in
new internal/redistest package.

Bonus edit: add package import comments.
Add connection mux to redisx.
Without that thing, go 1.3.3 says 'unexpected range'.
Merge pull request #91 from bearstech/fix_unexpected_range

Do not use 1.4 for range { } syntax.
Add Travis config.