Release v1.5.2

[thobrla]

No description provided.

[dhermes]

For my reference:

$ git log -1 --pretty=%H  # What is HEAD at time of doing "log"
42279caa52d3222dec460f923ad0c0e94b04eacb
$ git log v1.5.1..HEAD \
> | grep 'Merge pull request ' \
> | awk -F ' ' '{print $4}' \
> | sort

yields

#305
#306
#308
#310
#311
#312
#313
#314
#316
#318
#322
#324
#328
#329
#330
#336
#340

[dhermes]

LGTM

[dhermes]

@thobrla https://github.com/google/oauth2client/releases/tag/v1.5.2 created and waiting on

https://travis-ci.org/google/oauth2client/builds/91903047

to push to PyPI (i.e. that Travis job will actually deploy the new version automatically)