Don't tab stop on Hack links in proposal creation

It's really annoying when you are adding a proposal and you hit tab and
end up on the link to the Hack website. There's no need for this and at
least on newer browsers we can pretty easily skip the links for tab.

Unfortunately because this is model text it generates migrations. As we
know these migrations don't actually do anything, so they are annoying
but not actually harmful.

vendor/symposion/constants.py

@@ -1,5 +1,5 @@
 TEXT_FIELD_MONOSPACE_NOTE=(
     "This field is rendered with the monospace font "
-    "<a href=\"https://sourcefoundry.org/hack/\">Hack</a> with "
+    "<a tabindex=\"-1\" href=\"https://sourcefoundry.org/hack/\">Hack</a> with "
     "whitespace preserved")
 

vendor/symposion/proposals/migrations/0003_auto_20170702_2250.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.3 on 2017-07-02 12:50
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('symposion_proposals', '0002_auto_20170702_2233'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='proposalbase',
+            name='abstract',
+            field=models.TextField(help_text='This will appear in the conference programme. Up to about 500 words. This field is rendered with the monospace font <a tabindex="-1" href="https://sourcefoundry.org/hack/">Hack</a> with whitespace preserved', verbose_name='Abstract'),
+        ),
+        migrations.AlterField(
+            model_name='proposalbase',
+            name='private_abstract',
+            field=models.TextField(help_text='This will only be shown to organisers and reviewers. You should provide any details about your proposal that you don\'t want to be public here. This field is rendered with the monospace font <a tabindex="-1" href="https://sourcefoundry.org/hack/">Hack</a> with whitespace preserved', verbose_name='Private Abstract'),
+        ),
+        migrations.AlterField(
+            model_name='proposalbase',
+            name='technical_requirements',
+            field=models.TextField(blank=True, help_text='Speakers will be provided with: Internet access, power, projector, audio.  If you require anything in addition, please list your technical requirements here.  Such as: a static IP address, A/V equipment or will be demonstrating security-related techniques on the conference network. This field is rendered with the monospace font <a tabindex="-1" href="https://sourcefoundry.org/hack/">Hack</a> with whitespace preserved', verbose_name='Special Requirements'),
+        ),
+    ]

vendor/symposion/speakers/migrations/0004_auto_20170702_2250.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.3 on 2017-07-02 12:50
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('symposion_speakers', '0003_auto_20170702_1606'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='speaker',
+            name='accessibility',
+            field=models.TextField(blank=True, help_text='Please describe any special accessibility requirements that you may have. This field is rendered with the monospace font <a tabindex="-1" href="https://sourcefoundry.org/hack/">Hack</a> with whitespace preserved', verbose_name='Accessibility requirements'),
+        ),
+        migrations.AlterField(
+            model_name='speaker',
+            name='biography',
+            field=models.TextField(blank=True, help_text='This will appear on the conference website and in the programme.  Please write in the third person, eg \'Alice is a Moblin hacker...\', 150-200 words. This field is rendered with the monospace font <a tabindex="-1" href="https://sourcefoundry.org/hack/">Hack</a> with whitespace preserved', verbose_name='Biography'),
+        ),
+        migrations.AlterField(
+            model_name='speaker',
+            name='experience',
+            field=models.TextField(blank=True, help_text='Have you had any experience presenting elsewhere? If so, we\'d like to know. Anything you put here will only be seen by the organisers and reviewers; use it to convince them why they should accept your proposal. This field is rendered with the monospace font <a tabindex="-1" href="https://sourcefoundry.org/hack/">Hack</a> with whitespace preserved', verbose_name='Speaking experience'),
+        ),
+    ]