Boilerplate for the XPath lexer.
Cleaned up XPath lexer boilerplate a bit.
Basic working XPath lexer.

This doesn't lex everything of the XPath specification just yet and needs more
tests.
Added a few more XPath lexer tests.
XPath lexer test for predicates using axes.
Tweak Gemspec file list a bit.

This ensures it also takes files such as "Rakefile" into account when needed.
Support for lexing XPath wildcard expressions.

To support this we need to require whitespace around the "*" operator. This is
not ideal but it will do for now.
Basic XPath parser setup.
Added T_STAR as an XPath parser token.
Upgrade to RSpec 3.0.

For this I've enabled both the old expectation and stubbing/mocking syntax. The
old syntax is much more compact and to me reads nicer. For example, consider
the following:

    lex('<foo></foo>').should == [...]

To me this reads much nicer than this:

    expect(lex('<foo></foo>')).to eq([...])
Corrected docs of the xpath lexer.
Lex XPath operators using individual tokens.

Instead of lexing every operator as T_OP they now use individual tokens such as
T_EQ and T_LT.
Support for parsing basic XPath expressions.
Lexer specs for the various XPath axes.
Namespaced benchmarks per parser category.
Namespaced the profile directories.
Simple benchmarks for the XPath lexer.
Renamed the XPath axes_spec file.
Added XPath parser specs for all axes.
Use (name) nodes for @foo axes.