Remove $LOAD_PATH modifications

[daniel-rikowski]

I was investigating the slow startup performance of a Rails application using Bumbler (https://github.com/nevir/Bumbler)

I was quite surprised to always see ruby-units in place 1 or 2 as the worst offender, adding about 1 second to the total startup time.

After some investigation I noticed that this comes from an unfortunate interaction with the bootsnap gem (bootsnap improves the startup time of an app by caching and pre-scanning the load path, see https://github.com/Shopify/bootsnap#path-pre-scanning)

By modifying $LOAD_PATH twice, bootsnap requires rescans the whole load path twice by adding the current directory to the load path. The duration depends on the number of installed gems. In my case this is adding a considerable delay to the application startup.

ruby-units/lib/ruby-units.rb

Lines 1 to 2 in ec39140

	$LOAD_PATH << File.dirname(__FILE__)
	require_relative 'ruby_units/namespaced'

ruby-units/lib/ruby_units/namespaced.rb

Lines 1 to 5 in ec39140

	$LOAD_PATH << File.dirname(__FILE__)
	# require_relative this file to avoid creating an class alias from Unit to RubyUnits::Unit
	require_relative 'version'

Fortunately these modifications are not necessary, because require_relative is used which already considers the current directory.

My guess: previously require was used and the load path modifications were actually necessary. After switching to require_relative they became useless but weren't removed.

Anyway, this PR removes them.

[olbrich]

@daniel-rikowski Thanks for catching that!