removed computedproperties in favor of properties

There are several computed properties in main/modelx.py BaseX like
- ```created_ago```
- ```modified_ago```
- ```created_utc```
- ```modified_utc```

Computed properties ([1]) are both computed whenever read and saved in
the datastore for the purpose of indexing. The idea is that you can still
query on the field. This causes at least 3 additional writes per object
being written (1 for the data itself, 2 for index asc and desc).

Aside from causing additional writes there seems to be a problem: all
four are depending on self.modified and self.created which are
```DateTimeProperties``` ([2]). The values of ```auto_now``` and
```auto_now_add``` are only set when the model is written.
I experienced non deterministic ```None``` values of these in the
Datastore.

I see two other problems here:

1. ```created_ago``` and ```modified_ago``` just should never be saved
in the datastore, as ordering by these two just doesn't make any sense.
2. ```created_utc``` and ```modified_utc``` imply that the normal times
are saved in localtime. They're not, appengine uses UTC.

I suggest transforming all these into ordinary properties.

[1]: https://developers.google.com/appengine/docs/python/ndb/properties#computed
[2]: https://developers.google.com/appengine/docs/python/ndb/properties#Date_and_Time
also change avatar_url ComputedProperty to property
Merge pull request #1 from joernhees/fix-computedprops

Change ComputedProperty to property in BaseX
Added IE related meta tag
Footer changed to a fixed-height and it is pinned the bottom of the viewport
Removed relative dates and added Moment.js lib
Added Moment.js to README.md
Typo
Footer is using display table instead of box for vertical aligment
Updated util.param() to support list values
Moved run.py and package.json in the root
Update README.md to reflect the changes
Update CHANGESET.md
Fixed the bug in run.py when there were spaces in the path
Minor fix in run.py
Moved favicon.ico to the img directory and removed the gae-init logo
Updated the date in changeset
Update README.md
Added Client ID and Client Secret fields.
Added client id and client secret fields to Config.
Added github_id field to User.