stack-mode hangs emacs when using latest load-targets release

After upgrading to the latest `load-targets` release of `stack-ide`, `stack-mode` blocks emacs in various situations.
#### Versions
- stack: Version 0.1.5.0, Git revision f89f03c099c5405ed51462384cc60af5a62ade0a X86_64
- stack-ide: Version 0.1.0.0, Git revision bd7d845aa1654bca59a87aed44860c7b0e436031 (153 commits) X86_64
#### Problem 1

On initial startup, `stack-mode` blocks emacs indefinitely. This can be unblocked by hitting `C-g` numerous times.

The resulting `*stack:project*` buffer looks like this (those are `^H` characters):

```
Stack backend isn't ready. Waiting (0 attempts) ...
Flycheck tried to use the Stack backend, but the Stack backend isn't started yet. Starting it ...
Set initial command.
Starting: ("stack:project" nil "stack" "ide" "start" "package")
Running Flycheck with Stack backend ...
<- Progress: 0/2������������� �������������statistics-0.13.2.3: configure
<- Progress: 0/2������������� �������������statistics-0.13.2.3: build
<- Progress: 0/2������������� �������������statistics-0.13.2.3: install
<- Progress: 0/2������������� �������������Progress: 1/2������������� �������������criterion-1.1.0.0: configure
<- Progress: 1/2������������� �������������criterion-1.1.0.0: build
<- Progress: 1/2������������� �������������criterion-1.1.0.0: install
<- Progress: 1/2������������� �������������Completed all 2 actions.
```
#### Problem 2

After `C-g`-ing the first hang, running anything like `(stack-mode-goto)` hangs emacs in the same manor as above.

`C-g`-ing that adds only one new line to the `*stack:project*` buffer:

```
[nil] ~> {"tag":"RequestGetSpanInfo","contents":{"spanFilePath":"lib\/src\/Project\/File.hs","spanFromLine":27,"spanFromColumn":31,"spanToLine":27,"spanToColumn":43}}
```

This is reproducible.