Fix logo urls on v3 (#5081)

Author: Sayam753

README.rst

@@ -1,4 +1,4 @@
-.. image:: https://cdn.rawgit.com/pymc-devs/pymc3/master/docs/logos/svg/PyMC3_banner.svg
+.. image:: https://cdn.rawgit.com/pymc-devs/pymc/v3/docs/logos/svg/PyMC3_banner.svg
     :height: 100px
     :alt: PyMC3 logo
     :align: center

docs/source/semantic_sphinx/layout.html

@@ -54,7 +54,7 @@
     <div class="ui container">
         <div class="ui large secondary pointing menu">
             <a class="item" href="/">
-                <img class="ui bottom aligned tiny image" src="https://cdn.rawgit.com/pymc-devs/pymc3/master/docs/logos/svg/PyMC3_banner.svg" />
+                <img class="ui bottom aligned tiny image" src="https://cdn.rawgit.com/pymc-devs/pymc/v3/docs/logos/svg/PyMC3_banner.svg" />
             </a>
             {% if
             theme_navbar_links %} {%- for link in theme_navbar_links %} <a href="{{ pathto(*link[1:]) }}" class="item">{{
@@ -74,7 +74,7 @@
     </div>
     {% if pagename == 'index' %}
     <div class="ui center aligned text container">
-        <img src="https://cdn.rawgit.com/pymc-devs/pymc3/master/docs/logos/svg/PyMC3_banner.svg" />
+        <img src="https://cdn.rawgit.com/pymc-devs/pymc/v3/docs/logos/svg/PyMC3_banner.svg" />
         <h2>Probabilistic Programming in Python</h2>
         <a href="pymc-examples/examples/pymc3_howto/api_quickstart.html">
             <div class="ui huge primary button">Quickstart <i class="right arrow icon"></i></div>