Update twig/twig requirement from ^2.12 to ^3.0

[dependabot-preview]

Updates the requirements on twig/twig to permit the latest version.

Changelog

Sourced from twig/twig's changelog.

• 3.0.0 (2019-11-15)

• fixed number formatter in Intl extra extension when using a formatter prototype

• 3.0.0-BETA1 (2019-11-11)

• removed the "if" condition support on the "for" tag

• made the in, <, >, <=, >=, ==, and != operators more strict when comparing strings and integers/floats

• removed the "filter" tag

• added type hints everywhere

• changed Environment::resolveTemplate() to always return a TemplateWrapper instance

• removed Template::__toString()

• removed Parser::isReservedMacroName()

• removed SanboxedPrintNode

• removed Node::setTemplateName()

• made classes maked as "@​final" final

• removed InitRuntimeInterface, ExistsLoaderInterface, and SourceContextLoaderInterface

• removed the "spaceless" tag

• removed Twig\Environment::getBaseTemplateClass() and Twig\Environment::setBaseTemplateClass()

• removed the "base_template_class" option on Twig\Environment

• bumped minimum PHP version to 7.2

• removed PSR-0 classes

• 2.12.3 (2019-XX-XX)

• fixed number formatter in Intl extra extension when using a formatter prototype

• 2.12.2 (2019-11-11)

• added supported for exponential numbers

• 2.12.1 (2019-10-17)

• added the String extension in the "extra" repositories: "u" filter

• 2.12.0 (2019-10-05)

• added the spaceship operator ("<=>"), useful when using an arrow function in the "sort" filter

• added support for an "arrow" function on the "sort" filter

• added the CssInliner extension in the "extra" repositories: "inline_css"
  filter

• added the Inky extension in the "extra" repositories: "inky_to_html" filter

• added Intl extension in the "extra" repositories: "country_name",
  "currency_name", "currency_symbol", "language_name", "locale_name",
  "timezone_name", "format_currency", "format_number",
  "format_*_number", "format_datetime", "format_date", and "format_time"
  filters, and the "country_timezones" function

• added the Markdown extension in the "extra" repositories: "markdown_to_html",
  and "html_to_markdown" filters

• added the HtmlExtension extension in the "extra" repositories: "date_uri"

... (truncated)

Commits

• 9b58bb8 Prepare the 3.0.0 release
• e2f3e2e Update CHANGELOG
• 566305d Merge branch '2.x' into 3.x
• 34a2a74 bug #3198 Fix number formatter in Intl extra extension (fabpot)
• a6cf3f3 Fix number formatter in Intl extra extension
• d796e12 minor #3197 Fix README (fabpot)
• ddad9d8 Fix README
• 504f124 Merge branch '2.x' into 3.x
• 208b745 Fix docs
• 37bd13d Merge branch '1.x' into 2.x
• Additional commits viewable in compare view

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[dependabot-preview]

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