build with system calls instead of FileUtils

[TSMMark]

Thanks for your really great work on this gem! Helped me to get ruby running on lambda in no time. At Vydia we will be productionalizing ruby code on lambda in no time, and I'd love to be able to use this gem and contribute back to it as we learn more moving forward.

However, I ran into some interesting anomalous behavior during rumbda build, which this PR should alleviate. I also added --clean and --deployment flags to the bundle install command during build.

Anomalous FileUtils behavior

FileUtils truncating dest rb files

I have no explanation for why this was happening, but it was consistent and very frustrating. I tried using :verbose => true option, nothing. Tried rewriting using FIleUtils in many different ways, nothing. After spending hours with no results I gave up on FileUtils and rewrote using system calls.

Whole source file:

Truncated dest file:

FileUtils using stale versions of source files

No matter what cache I clear, how many times restarting the machine, this line https://github.com/kleaver/rumbda/blob/cda8f9d3cf296c38fa389ac0c906ca166750e999/lib/rumbda/build.rb#L18 consistently only results in stale versions of the file being copied to dest. The only workaround was to rename the file, which would work one time, but then making changes to that file have the same results after any updates are made. :goberserk:

Modified source file:

Unmodified dest file:

Success!

Using this commit's patch version in my Gemfile,

group :development do
  gem "rumbda", :github => "Vydia/rumbda", :ref => "19e3016e2d3659a771c0a6933e4e4b3a51561eef"
end

here we are, running on lambda finally. Changes respected, truncation ceased, and gems cleaned.

[TSMMark]

Travis build failed on unrelated bundler version issue:

$ bundle install --jobs=3 --retry=3 --without development
Fetching gem metadata from https://rubygems.org/..........
Fetching gem metadata from https://rubygems.org/.
Resolving dependencies...
Bundler could not find compatible versions for gem "bundler":
  In Gemfile:
    rumbda was resolved to 1.2.0.SNAPSHOT, which depends on
      bundler (= 1.9.9)
  Current Bundler version:
    bundler (1.16.1)
This Gemfile requires a different version of Bundler.
Perhaps you need to update Bundler by running `gem install bundler`?
Could not find gem 'bundler (= 1.9.9)', which is required by gem 'rumbda', in
any of the sources.
The command "bundle install --jobs=3 --retry=3 --without development" failed and exited with 6 during .
Your build has been stopped.

You could try gem uninstall bundler -v 1.16.1 before gem install bundler -v 1.9.9. That works for me locally.

For the record, rumbda test suite passes for me locally:

▶ rake
/Users/mark/.rvm/rubies/ruby-2.2.2/bin/ruby -I/Users/mark/.rvm/gems/ruby-2.2.2/gems/rspec-core-3.7.1/lib:/Users/mark/.rvm/gems/ruby-2.2.2/gems/rspec-support-3.7.1/lib /Users/mark/.rvm/gems/ruby-2.2.2/gems/rspec-core-3.7.1/exe/rspec --pattern spec/\*\*\{,/\*/\*\*\}/\*_spec.rb
......Creating zip file.
.

Finished in 0.03574 seconds (files took 0.17257 seconds to load)
7 examples, 0 failures