* Int64(int value) should not be sensitive to rounding errors

* fix error in test

* fix constructor

* new package version number

Cleanup

BUG=
R=rnystrom@google.com

Review-Url: https://codereview.chromium.org//2979043002 .

Also adding a CHANGELOG and analysis_options since it's strong mode
clean now.

R=cbracken@google.com, leafp@google.com

Review URL: https://codereview.chromium.org//1963283002 .

Includes performance fixes and error tests.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1834783004 .