call graph: changed color of arrows/edges to grey for readability

call graph: changed color of arrows/edges to grey for better 
readability of the labels
Ignore build artifacts from Git
Missing config.m4 and tests from Git ignore
fixes PR #20 when using randomly generated run ids (better patch by @slava-vishnyakov)
Merge pull request #29 from robocoder/patch-2

fixes PR #20 when using randomly generated run ids
Merge pull request #25 from erikwebb/add-gitignore

Ignore build artifacts from Git
Merge pull request #23 from oliworx/patch-1

call graph: changed color of arrows/edges to grey for readability