Merge pull request #63 from glogiotatidis/master

[bug 1063585] Lowercase tagName before comparing with 'a'.
[fix bug 1066865] Ignore snippets that link to about:accounts when sync is setup.
Merge pull request #64 from glogiotatidis/accounts-oldsync

[fix bug 1066865] Ignore snippets that link to about:accounts when sync is setup.
Fix bug 1078006: Don’t concat on HTMLCollection.

Instead we want to add to the existing array.
Increase max_length of all RegexFields to 255.
[fix bug 1067324] Custom snippet metrics.
Merge pull request #68 from glogiotatidis/metric-3

[fix bug 1067324] Custom snippet metrics.
Add travis.
Merge pull request #69 from glogiotatidis/travis

Add travis.
Update README.md
Update preview template to match fetch_snippets.html.
Add ability to filter snippets by their template.
Stop hiding Client Match Rules on the snippet admin page.

Because Every time I open that section I wish I didn’t have to.
Merge pull request #74 from Osmose/stop-hiding-cmrs

Stop hiding Client Match Rules on the snippet admin page.
Merge pull request #70 from Osmose/filter-by-template

Add ability to filter snippets by their template.
Add the ability to use a checkbox for a boolean template variable.
Remove instant preview from the snippet admin form.

The instant preview has a few issues:

- Occasional errors due to weird iframe back-forward behavior.
- Slowness in editing large snippets due to constant sending of snippet
  data, as well as from snippets that take up some CPU.
- Restrictions on functionality due to being in an iframe.

Thus I’ve removed the iframe and the instant preview and added a button
to trigger a preview in a new tab.
Allow use of snippet_id in template variables.

Now the snippet ID can be included in either a snippet template or the
template data stored on a snippet. Mostly useful for Raw code snippets
that still want to access the snippet ID.
Upgrade factoryboy to version 2.4.1.
[fix bug 1082208] Support media files and CDN.