Update to 1.53

Upstream changes:
1.53 08 Jul 2016

- Fix 'Illegal division by zero' when x_min_value and x_max_value
  are defined and x_tick_number set to 'auto' RT#73185
  Thanks to Bob Rogers, https://github.com/ruz/GDGraph/pull/12

1.52 28 Jan 2016

- y1_min_range and y2_min_range instead of min_range_1 and min_range_2,
  niether were documented before.
- Update documentation in regards to all *_min_range options available.

1.51 27 Dec 2015

- fix shadows rendering on cumulative bar charts
  thanks to https://github.com/Tordek
  see https://github.com/ruz/GDGraph/pull/4

1.50 27 Dec 2015

- run samples as part of test suite to make sure no sample crashes
  thanks to https://github.com/tynovsky
- properly define test requirements using newer MakeMaker

1.49 11 Mar 2015

- fix to Z-axis color filling in 3D pie charts (Debian Bug #489184)
- bump ExtUtils::MakeMaker dependency
- tiny improvement in the code of the samples

(wen)