Anglicize and fix typos for the Adapter design pattern page.

[nepsilon]

I saw and fixed 5 typos in the page at chapters/design_patterns/adapter.md.
I also rewrote the problem statement as I found it hard to understand for an English readership.

[sukima]

I have an example for the intro.

I wanted to write a library which would communicate over the network. However the actual implementation of the network code is different between environments (Browser, Node.js, Titanium, etc.)

class NetworkAdapter
  send: (data) ->

class BrowserNetworkAdapter extends NetworkAdapter
  send: (data) ->
    # Do something with XMLHtttpRequest object.

class TitaniumNetworkAdapter extends NetworkAdapter
  send: (data) ->
    # Do something with Ti.Network.HttpClient object.

[peterhellberg]

@nepsilon Thank you for the changes, I’ll now merge this and add you to the contributors team.

[tashemi]

@nepsilon thanks for typos correction and anglicizing