Documentation fix

* Fixes bug in documentation and converts examples to doctests to ensure
  examples will actually run (closes #34).

docs/using.rst

@@ -21,90 +21,93 @@ are e.g. the wiki page or the XMP Specification Part 1 available from:
 
 Method 1: Read XMP
 ------------------
-One of the most basic uses of the library is::
+One of the most basic uses of the library is:
 
-	from libxmp import *
+>>> from libxmp.utils import file_to_dict
+>>> xmp = file_to_dict( "test/samples/BlueSquare.xmp" )
 
-	xmp = file_to_dict( "/path/to/some/file_with_xmp.ext" )
 
 This will read the XMP embedded in the file and return it as a
 dictionary. The keys in the dictionary are XMP namespaces so to e.g. get
-all Dublin Core properties use::
+all Dublin Core properties use:
+
+
+>>> from libxmp import consts
+>>> dc = xmp[consts.XMP_NS_DC]
+
+or to be explicit:
+
+>>> dc = xmp["http://purl.org/dc/elements/1.1/"]
 
-	dc = xmp[consts.XMP_NS_DC]
-	# or to be explicit
-	dc = xmp["http://purl.org/dc/elements/1.1/"]
-	
 This will give you a list of all Dublin Core properties, where each
-element in the list is a tuple such as::
-
-	( 
-		u'dc:format', 
-		u'application/vnd.adobe.photoshop', 
-		{
-			'IS_SCHEMA': False, 
-			'IS_ALIAS': False, 
-			'HAS_TYPE': False, 
-			'ARRAY_IS_ALT': False, 
-			'IS_INTERNAL': False, 
-			'IS_DERIVED': False, 
-			'HAS_ALIASES': False, 
-			'HAS_LANG': False, 
-			'VALUE_IS_STRUCT': False, 
-			'HAS_QUALIFIERS': False, 
-			'ARRAY_IS_ALTTEXT': False, 
-			'VALUE_IS_URI': False, 
-			'VALUE_IS_ARRAY': False, 
-			'ARRAY_IS_ORDERED': False, 
-			'IS_QUALIFIER': False, 
-			'IS_STABLE': False
-		}
-	)
-	
-The first element is the property name, the second element is the value
-and the third element is options associated with the element (describing
-e.g the type of the property).
+element in the list is a tuple. The first element is the property name,
+the second element is the value and the third element is options associated
+with the element (describing e.g the type of the property):
+
+First tuple element:
+
+>>> print(dc[0][0])
+dc:format
+
+Second tuple element:
+
+>>> print(dc[0][1])
+application/vnd.adobe.photoshop
+
+Third tuple element is a dict with options:
+
+>>> dc[0][2]['IS_SCHEMA']
+False
 
 Method 2: Read/Write XMP
 ------------------------
 Example 1 focused on just extracting the XMP from a file an determine the
 value of a property. If you however want to extract the XMP from a file,
-update it, *and* write it back again you need to do like the following::
-
-
-	from libxmp import *
-
-	# Read file
-	xmpfile = XMPFiles( file_path="/path/to/some/file", open_forupdate=True )
-	
-	# Get XMP from file.
-	xmp = xmpfile.get_xmp()
-	
-	# Print the property dc:format 
-	print xmp.get_property( libxmp.consts.XMP_NS_DC, 'format' )
-	
-	# Change the XMP property
-	xmp.set_property( libxmp.consts.XMP_NS_DC, 'format','application/vnd.adobe.illustrator' )
-	
-	# Check if XMP document can be written to file and write it.
-	if xmpfile.can_put_xmp(xmp):
-		xmpfile.put_xmp(xmp)
-		
-	# XMP document is not written to the file, before the file 
-	# is closed.
-	xmpfile.close_file()
+update it, *and* write it back again you need to do like the following
+
+Read file:
+
+>>> from libxmp import XMPFiles, consts
+>>> xmpfile = XMPFiles( file_path="test/samples/BlueSquare.jpg", open_forupdate=True )
+
+Get XMP from file:
+
+>>> xmp = xmpfile.get_xmp()
+
+Print the property ``dc:format``:
+
+>>> print(xmp.get_property(consts.XMP_NS_DC, 'format' ))
+image/jpeg
+
+Change the XMP property:
+
+>>> xmp.set_property(consts.XMP_NS_DC, u'format', u'application/vnd.adobe.illustrator' )
+>>> print(xmp.get_property(consts.XMP_NS_DC, 'format' ))
+application/vnd.adobe.illustrator
+
+Check if XMP document can be written to file and write it:
+
+>>> xmpfile.can_put_xmp(xmp)
+True
+
+XMP document is not written to the file, before the file
+is closed:
+
+>>> xmpfile.close_file()
 
 Further Examples
 -------------
 Append an array item to the XMP packet.::
 
-	from libxmp import *
-	
-	# Read file
-	xmpfile = XMPFiles( file_path="/path/to/some/file" )
-	
-	# Get XMP from file
-	xmp = xmpfile.get_xmp()
-	
-	# Create a new array item and append a value
-	xmp.append_array_item(files.XMP_NS_DC, 'creator', 'Your Name Here', {'prop_array_is_ordered': True, 'prop_value_is_array': True})	
+Read file:
+
+>>> from libxmp import XMPFiles, consts
+>>> xmpfile = XMPFiles( file_path="test/samples/BlueSquare.xmp" )
+
+Get XMP from file:
+
+>>> xmp = xmpfile.get_xmp()
+
+Create a new array item and append a value:
+
+>>> xmp.append_array_item(consts.XMP_NS_DC, 'creator', 'Your Name Here', {'prop_array_is_ordered': True, 'prop_value_is_array': True})