Documentation generation fails on Python 2.6.9

The HTML parser blows up when trying to generate documentation for the first time on v2.6.9.

```
First run, creating autocomplete index...
Traceback (most recent call last):
File "/Users/guymonj/.pyenv/versions/2.6.9/bin/aws-shell", line 9, in
load_entry_point('aws-shell', 'console_scripts', 'aws-shell')()
File "/Users/guymonj/Code/aws-shell/awsshell/__init__.py", line 47, in main
write_index(index_file)
File "/Users/guymonj/Code/aws-shell/awsshell/makeindex.py", line 67, in write_index
index_command(current, help_command)
File "/Users/guymonj/Code/aws-shell/awsshell/makeindex.py", line 59, in index_command
index_command(child, sub_help_command)
File "/Users/guymonj/Code/aws-shell/awsshell/makeindex.py", line 59, in index_command
index_command(child, sub_help_command)
File "/Users/guymonj/Code/aws-shell/awsshell/makeindex.py", line 40, in index_command
arg_obj.documentation.split('\n')[0])
File "/Users/guymonj/Code/aws-shell/awsshell/utils.py", line 22, in remove_html
s.feed(html)
File "/Users/guymonj/.pyenv/versions/2.6.9/lib/python2.6/HTMLParser.py", line 108, in feed
self.goahead(0)
File "/Users/guymonj/.pyenv/versions/2.6.9/lib/python2.6/HTMLParser.py", line 148, in goahead
k = self.parse_starttag(i)
File "/Users/guymonj/.pyenv/versions/2.6.9/lib/python2.6/HTMLParser.py", line 229, in parse_starttag
endpos = self.check_for_whole_start_tag(i)
File "/Users/guymonj/.pyenv/versions/2.6.9/lib/python2.6/HTMLParser.py", line 304, in check_for_whole_start_tag
self.error("malformed start tag")
File "/Users/guymonj/.pyenv/versions/2.6.9/lib/python2.6/HTMLParser.py", line 115, in error
raise HTMLParseError(message, self.getpos())
HTMLParser.HTMLParseError: malformed start tag, at line 1, column 275
```

The documentation causing the issue is `deploy push`:

> Required. Information about the location of the application revision to be uploaded to Amazon S3. You must specify both a bucket and a key that represent the Amazon S3 bucket name and the object key name. Content will be zipped before uploading. Use the format s3:///

Specifically: `Use the format s3://\/\` is being incorrectly interpreted as HTML
This can be seen on the online docs here:
http://docs.aws.amazon.com/cli/latest/reference/deploy/push.html
Which seems to strip the 'tags' to `Use the format s3:///`

This also affects the CLI docs as the parameter descriptions are missing after this option:

```
OPTIONS
--application-name (string) Required. The name of the AWS CodeDeploy
application to be associated with the application revision.

--s3-location (string)

--ignore-hidden-files | --no-ignore-hidden-files (boolean)

--source (string)

--description (string)
```

This appears to work properly on all other versions of Python (2.7, 3.3, 3.4, 3.5). The documentation on the CLI for these versions strips the documentation to `Use the format s3:///` much like the online docs, which is still not optimal.

Potentially related to #107, but this is a different error.