include segment name and file name for exception

[philippb]

When throwing an exception. include the file name and the segment ID so it's easier to find where the error is.

e.g.

Traceback (most recent call last):
  File "/Users/philipp/coding/ks-email-parser/venv/bin/ks-email-parser", line 9, in <module>
    load_entry_point('ks-email-parser==0.2.6', 'console_scripts', 'ks-email-parser')()
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/__init__.py", line 62, in main
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/__init__.py", line 31, in parse_emails
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/renderer.py", line 177, in render
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/renderer.py", line 102, in render
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/renderer.py", line 102, in <dictcomp>
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/renderer.py", line 83, in _render_placeholder
  File "/Users/philipp/coding/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/renderer.py", line 56, in _inline_css
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/xml/etree/ElementTree.py", line 1325, in XML
    parser.feed(text)
xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 6, column 24

[philippb]

segment ID is the name of the string.

<string name"segment_id">Content</string>

[snejku]

@philippb, @ca77y
New sample output

$ ks-email-parser
F.....
ERRORS:
1. Unable to read content from /Users/snejku/keepsafe/ks-email-parser/src/en/email.xml
not well-formed (invalid token): line 5, column 28
Segment ID: content
_______________
    <string name="content"><<Dummy content</string>
                            ^
Traceback (most recent call last):
  File "/Users/snejku/keepsafe/ks-email-parser/venv/lib/python3.4/site-packages/ks_email_parser-0.2.6-py3.4.egg/email_parser/reader.py", line 67, in read
    tree = ElementTree.parse(email_path)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/xml/etree/ElementTree.py", line 1186, in parse
    tree.parse(source, parser)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/xml/etree/ElementTree.py", line 598, in parse
    self._root = parser._parse_whole(source)
  File "<string>", line None
xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 5, column 28

All done

[ca77y]

Looks good