Upated test cases to support compilation halting on first failed compiler. Updated existing tests to handle CompileError being thrown on failure.

Updated compile tasks to raise exceptions after compiling all files
Updated tests to verify exceptions raised
Always load paths on app.start, even with --no-compile
Move the Elixir version requirement check to a better place
Merge pull request #1452 from meh/mix-version

Move the Elixir version requirement check to a better place
Document mix loadpaths and app.start options
Merge pull request #1449 from jwarwick/issue_1441

Possible fix for Issue #1441
Slight clean up on mix tests

We don't need to test all scenarios because guaranteeing that
a failure in one compiler is enough to abort the others is enough
for an integration test.
Fixed doc typos in Mix.Tasks.Escriptize
Merge pull request #1453 from jwarwick/escript_docs

Fixed doc typos in Mix.Tasks.Escriptize
Issue #1448, Mix.Tasks.Compiler.*.manifests returns complete path
Merge pull request #1454 from jwarwick/issue_1448

Issue #1448, Mix.Tasks.Compiler.*.manifests returns complete path
Watch the target directory on compilation
Remove deprecations pre 0.10.0
Support for multiple callbacks in parallel compiler
Support each_module callback on ParallelCompiler
Initial work on ManifestCompiler that tracks dependencies in the manifest for quick compilation
Improve ManifestCompiler to track more dependencies
Put old beam files back if compilation fails
Just preload files if something is stale