Fix cabal file referencing old changelog name
Update Travis CI Job
Add/update hackage/travis shields in README.md
Build Haddock documentation for System.Process.Internals

From my perspective the module name already clearly states that this is
internal stuff + currently we have a 404 on Hackage for this one + I
actually want to read the Haddocks.

Fixes #7
Add `/dist/` to `.gitignore`
Adapt documentation of `readProcess`

(a program does not have a standard input)
Document that `readProcess` works with relative paths
Move docs on semantics for raw commands from `proc` to `RawCommand`

(This is where it belongs to, IMHO.)

Closes #8
Add IsString instance for CmdSpec