Add generic server

This is useful if you want to build servers that talk the Redis protocol

Note: this is a work in progress and it's likely to change a lot during development.
Loop on client until disconnected
Move server into its own directory
Expose Write* methods
Add ERR prefix when writing errors
Add Client struct to hold connections
Merge branch 'master' into server

* master:
  Add travis-ci support for CI testing
Fix package name
Add type Reader and Read function

A Redis server can only read from a client a multi-bulk request,
anything else will be an error.

The Redis protocol is well defined, where each multi-bulk request will
comply with this format:

* '*' character
* the number of bulks following
* \r\n

Each bulk will follow, with the following format:

* '$'
* the number of bytes of the data
* \r\n
* n-bytes of data
* \r\n

This might eventually be adapted to the Gedis parser.
Add benchmark for Read
Add documentation for gedis.Server
Add ParseError struct
Add missing test
Refactor ParseError
Add server README from godoc
Merge branch 'server'

* server:
  Add server README from godoc
  Refactor ParseError
  Add missing test
  Add ParseError struct
  Add documentation for gedis.Server
  Add benchmark for Read
  Add type Reader and Read function
  Fix package name
  Add Client struct to hold connections
  Add ERR prefix when writing errors
  Expose Write* methods
  Move server into its own directory
  Loop on client until disconnected
  Add generic server
Add LICENSE file