Fix miscellaneous Sphinx warnings (#244)

* /index.rst:24: WARNING: Line block ends without a blank line.

* /install.rst:300: WARNING: Explicit markup ends without a blank line; unexpected unindent.

* /admin.rst:273: WARNING: Could not lex literal_block as "http". Highlighting skipped.

* /tutorials/tut1.rst:150: WARNING: Could not lex literal_block as "json". Highlighting skipped.

* Remove extra newline

* Use integer value as epoch in JSON snippet

Even though using a string value is convenient (due to the lack of JSON
comments), it is confusing since the value should actually be an
integer. A slightly more verbose documentation is therefore preferable.

admin.rst

@@ -272,7 +272,7 @@ As discussed in :ref:`singular_plural`, there are no special URL forms for singu
 
 .. code:: http
 
-  GET /people?id=eq.1
+  GET /people?id=eq.1 HTTP/1.1
   Accept: application/vnd.pgrst.object+json
 
 This allows compound primary keys and makes the intent for singular response independent of a URL convention.