Use executable's directory rather than working directory in examples

[cztomczak]

See the main_linux.go and main_windows.go files.

Daniel Theophanes suggested to use something like this:
https://bitbucket.org/kardianos/osext/src

On Windows the executable's path can be obtained by a call to GetModuleFileNameW().

Though I don't see an example for Linux in the link above.

[cztomczak]

Ahhh, here is Linux:
https://bitbucket.org/kardianos/osext/src/364fb577de68fb646c4cb39cc0e09c887ee16376/osext_procfs.go?at=default

[cztomczak]

OS X example is using executable's directory.