CHANGELOG: Add changelog for 2.0.5 (pingcap#7005)

*: support parallel hash agg (pingcap#6658)

CHANGELOG: Add changelog for 2.0.4 (pingcap#6846)

add pull request template (pingcap#6718)

Add change logs for 2.0.x (pingcap#6725)

Add change logs for 2.0/2.0.1/2.0.2/2.0.3

sessionctx/binloginfo: add a timeout for writing binlog (pingcap#6588)

tidb-server: don't bind graceful shutdown to SIGTERM (pingcap#6562) (p…

…ingcap#6569)

SIGTERM is the default kill command signal, it's better to bind it
with normal exit rather than graceful shutdown.

update container builder image to use golang 1.10.1 (pingcap#6410) (p…

…ingcap#6412)

[release-1.0] cherry pick add manual gc (pingcap#6326)

ddl: support the rolling upgrade. (pingcap#6301) (pingcap#6305)