Fix -tags processing in packagesAndTestargs

Also, added a couple of tests. More to come later.

Fixes #45
Use drone.io for CI
Skip packages without tests
Merge pull request #46 from pjvds/master

Skip packages without tests
Add gocov-xml
Merge pull request #47 from AlekSi/patch-1

Add gocov-xml
Rename gocov import name to avoid conflict.
Merge pull request #50 from t-yuki/avoid-importpath-conflict

Gocov fails if the target imports gocov itself.
Temporarily rename PkgObjs of instrumented packages

Fixes #51
Add package parallel flag

* Add the '-p' flag to control running packages in parallel
* See golang.org/src/cmd/go/testflag.go for details
Update -p default to GOMAXPROCS(0)
Update command descriptions, -p default
Drop "gocov test", introduce "gocov convert"

Gocov no longer includes the means of instrumenting
source code; go tool cover must be used instead.

What gocov now provides is a stop-gap until other
packages are able to use go tool cover directly.
In the meantime, gocov provides a "convert" command
to convert a cover profile into gocov's JSON
interchange format.
Reinstate gocov test

Dumb idea; that'll break existing CI scripts
Fix copy/paste
added red color to misses and a flag to turn this on (off by default)
ran gofmt
no ANSI codes by default and removed 'MISS' from miss lines
fixed spelling of 'Differentiate'
Lowercased coverage in usage string