mypy: Update mypy to a version from master.

We want to be able to take advantage of some new features added
to dmypy.

requirements/dev.txt

@@ -9,6 +9,7 @@
 #
 --no-binary psycopg2
 
+git+https://github.com/python/mypy.git@6a934d32124991a77ea433856cf2d62871ceb632#egg=mypy==0.610+dev.6a934d32124991a77ea433856cf2d62871ceb632
 git+https://github.com/zulip/talon.git@7d8bdc4dbcfcc5a73298747293b99fe53da55315#egg=talon==1.2.10.zulip1
 git+https://github.com/zulip/ultrajson@70ac02bec#egg=ujson==1.35+git
 git+https://github.com/zulip/python-zulip-api.git@0.4.6#egg=zulip==0.4.6_git&subdirectory=zulip
@@ -90,7 +91,6 @@ markdown==2.6.11
 markupsafe==1.0
 mock==2.0.0
 moto==1.3.3
-mypy==0.600
 mypy_extensions==0.3.0
 ndg-httpsclient==0.5.0
 oauth2client==4.1.2
@@ -169,7 +169,7 @@ traitlets==4.3.2          # via ipython
 transifex-client==0.12.5
 twilio==6.13.0
 twisted==18.4.0
-typed-ast==1.1.0          # via mypy
+typed-ast==1.1.0
 typing==3.6.4
 uritemplate==3.0.0
 urllib3==1.22             # via requests, transifex-client

requirements/mypy.in

@@ -2,7 +2,6 @@
 # /tools/update-locked-requirements to update requirements/dev.txt
 # and requirements/mypy.txt.
 # See requirements/README.md for more detail.
-mypy==0.600
-
+-e git+https://github.com/python/mypy.git@6a934d32124991a77ea433856cf2d62871ceb632#egg=mypy==0.610+dev.6a934d32124991a77ea433856cf2d62871ceb632
 # Include typing explicitly, since it's needed on Python 3.4
 typing==3.6.4

requirements/mypy.txt

@@ -7,6 +7,6 @@
 #
 # For details, see requirements/README.md .
 #
-mypy==0.600
-typed-ast==1.1.0          # via mypy
+git+https://github.com/python/mypy.git@6a934d32124991a77ea433856cf2d62871ceb632#egg=mypy==0.610+dev.6a934d32124991a77ea433856cf2d62871ceb632
+typed-ast==1.1.0
 typing==3.6.4