[MAINT] update travis badge and pin sphinx (#305)

* use sphinx major version 2

* point to travis.com instead of org

Author: jdkent

README.rst

@@ -34,9 +34,9 @@ for links to render properly.
 .. |joss| image:: https://joss.theoj.org/papers/10.21105/joss.01295/status.svg
    :target: https://doi.org/10.21105/joss.01295
 
-.. |travis| image:: https://travis-ci.org/HBClab/NiBetaSeries.svg?branch=master
+.. |travis| image:: https://travis-ci.com/HBClab/NiBetaSeries.svg?branch=master
     :alt: Travis-CI Build Status
-    :target: https://travis-ci.org/HBClab/NiBetaSeries
+    :target: https://travis-ci.com/HBClab/NiBetaSeries
 
 .. |codecov| image:: https://codecov.io/github/HBClab/NiBetaSeries/coverage.svg?branch=master
     :alt: Coverage Status

setup.cfg

@@ -64,7 +64,7 @@ dev =
     codecov
     coverage
 doc = 
-    sphinx > 2
+    sphinx > 2,< 3
     sphinx_rtd_theme
     sphinx-argparse
     sphinx-gallery