fixed version parsing for Windows and EnterpriseDB

[marcinbudny]

Fixes #142

[coveralls]

Coverage remained the same at 54.701% when pulling 3fd55f1 on marcinbudny:master into 5b9fea0 on wrouesnel:master.

[marcinbudny]

I'm new to golang and I'm not really sure why the build fails. The output at one point says:

postgres_exporter_test.go:1::warning: file is not gofmted with -s (gofmt)
make: *** [style] Error 1
The command "make all" exited with 2.

However when I run go fmt locally, files are not changed. The output does not specify any other broken rule. Any help?

[wrouesnel]

@marcinbudny run "make fmt" instead.

[marcinbudny]

@wrouesnel That helped, thanks

[wrouesnel]

Looks great! Appreciate the tests - merging.