Add webview support for kivy-ios. Any URL can be opened in webview by
just doing the following:
```
import ios
url = "http://www.google.com"
ios.IOSWebView().open(url)
```
Tested:OK
If I try download the archive manually, this url "http://vorboss.dl.sourceforge.net/project/libpng/libpng16/1.6.24/libpng-1.6.24.tar.gz" redirect to "https://sourceforge.net/projects/libpng/files/"
...
Extract libpng
Extract libpng for i386
Traceback (most recent call last):
File "./toolchain.py", line 1311, in <module>
ToolchainCL()
File "./toolchain.py", line 1082, in __init__
getattr(self, args.command)()
File "./toolchain.py", line 1106, in build
build_recipes(args.recipe, ctx)
File "./toolchain.py", line 974, in build_recipes
recipe.execute()
File "/Users/prrcarvalho/Development/kivy-ios-master/toolchain.py", line 585, in execute
self.extract()
File "/Users/prrcarvalho/Development/kivy-ios-master/toolchain.py", line 56, in _cache_execution
f(self, *args, **kwargs)
File "/Users/prrcarvalho/Development/kivy-ios-master/toolchain.py", line 621, in extract
self.extract_arch(arch.arch)
File "/Users/prrcarvalho/Development/kivy-ios-master/toolchain.py", line 625, in extract_arch
dest_dir = join(build_dir, self.archive_root)
File "/Users/prrcarvalho/Development/kivy-ios-master/toolchain.py", line 577, in archive_root
value = self.get_archive_rootdir(self.archive_fn)
File "/Users/prrcarvalho/Development/kivy-ios-master/toolchain.py", line 442, in get_archive_rootdir
archive = tarfile.open(filename)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py", line 1673, in open
return func(name, "r", fileobj, **kwargs)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py", line 1738, in gzopen
fileobj = gzip.GzipFile(name, mode, compresslevel, fileobj)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/gzip.py", line 94, in __init__
fileobj = self.myfileobj = __builtin__.open(filename, mode or 'rb')
IOError: [Errno 2] No such file or directory: '/Users/prrcarvalho/Development/kivy-ios-master/.cache/libpng-libpng-1.6.24.tar.gz'
