Fixed typos and formatting issues in Mix.Tasks.CompileElixir
Fixed doc typos in Mix.Tasks.Compile.*
Merge pull request #1438 from jwarwick/mix_tasks

Fixed doc typos in Mix.Tasks.Compile.*
Add @protocol attribute to defimpl
Merge pull request #1439 from meh/protocol

Add @protocol attribute to defimpl
Ensure __impl__ follows the same convention as other dynamically generated info functions
Remove test at the wrong location
Improve docs for Mix.Deps
Check path deps to see if we should recompile

'mix compile' will check the manifest files' mtime of all mix path
dependencies - if they are newer then the local .compile.elixir file
we need to recompile.
Merge pull request #1435 from ericmj/mix-force-path-deps

Check mix path deps to see if we need recompile project
Only delete beam files with no source
Reduce cases where IEx parser can get stuck, closes #1443
Fixed minor typo in Mix.deps doc
Fixed doc typos and formatting in IO
Merge pull request #1444 from jwarwick/doc_typos

Fixed doc typos in Mix.deps and IO
Fixed typos in Kernel.ParallelCompiler docs
Merge pull request #1447 from jwarwick/compiler_typos

Fixed typos in Kernel.ParallelCompiler docs
Make Mix.SystemVersionError message more meaningful
Merge pull request #1450 from meh/mix-elixir

Make Mix.SystemVersionError message more meaningful
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