Fixed behavior of multi-step builds.

* Output from the main strawboss executable is properly directed to stdout
  and stderr.
* Added threshold logging to strawboss core functions.
* Fixed a bug in the way dependent steps were detected and executed.
  The logic for checking if prior steps had already been executed was only
  executed once when the initial step was prepared, not for any of the
  dependent steps. This logic has been moved into the main work block for
  executing steps.
* Renamed `initiateRun` to `run` and  `runStep` to `doRun` to be more accurate.
* Dependent steps get their owng, independent copy of the workspace.
* Updated the test project to provide a test target.

src/main/nim/strawboss.nim

@@ -8,8 +8,8 @@ let SB_VER = "0.2.0"
 
 proc logProcOutput*(outMsg, errMsg: TaintedString, cmd: string) =
   let prefix = if cmd != nil: cmd else: ""
-  if outMsg != nil: echo prefix & "(stdout): " & outMsg
-  if errMsg != nil: echo prefix & "(stderr): " & errMsg
+  if outMsg != nil: stdout.writeLine prefix & outMsg
+  if errMsg != nil: stderr.writeLine prefix & errMsg
 
 when isMainModule:
 
@@ -51,7 +51,7 @@ Options
 
       if req.workspaceDir.isNilOrEmpty: req.workspaceDir = mkdtemp()
 
-      let status = core.initiateRun(cfg, req, logProcOutput)
+      let status = core.run(cfg, req, logProcOutput)
       if status.state == BuildState.failed: raiseEx status.details
       echo "strawboss: build passed."
     except: