PlatformIO Library Manager manifest file

* This library in Web: http://platformio.ikravets.com/#!/lib/show/MSP430-Energia-HttpClient
* Specification: [PlatformIO Library Manager](http://docs.platformio.ikravets.com/en/latest/librarymanager/index.html)
* Integration: [IDE Integration](http://docs.platformio.ikravets.com/en/latest/ide.html)

`library.json` is a library manifest file which can be used with different tools/managers to organise embedded libraries. Currently, only [PlatformIO](http://platformio.ikravets.com) uses it.  How does this look from CLI:

```bash
$ platformio lib search "+msp430 http client"
# Found ... libraries:
# MSP430-Energia-HttpClient        HttpClient is a library to make it easier to interact with web servers from MSP430 using Energia

$ platformio lib install MSP430-Energia-HttpClient
# Installing MSP430-Energia-HttpClient  library:
# Downloading  [####################################]  100%
# Unpacking  [####################################]  100%
# The library ‘MSP430-Energia-HttpClient' has been successfully installed!

$ platformio lib show MSP430-Energia-HttpClient
# MSP430-Energia-HttpClient
# -------------
# Author: Zack Lalanne
# Keywords: http, web, client, ethernet
# Version: ***
#
# HttpClient is a library to make it easier to interact with web servers from MSP430 using Energia

$ platformio lib update
# Updating MSP430-Energia-HttpClient  library:
# Versions: Current=***, Latest=***       [Up-to-date]]
```
Merge pull request #1 from ivankravets/patch-2

PlatformIO Library Manager manifest file