tutorials + basic testing added

Upgrades include:

• basic test suite introduced (now has enough that the entire tutorial should work after installing from the source).
• New function has been added that calculates the ideal velocity pixel size for the user (also used in the tutorial).
• Initialisation stage and LSD function have been optimised. Runtimes had been reduced by 500%.

Bugs fixed include:

• reference_wave array was no longer gives 'unknown variable' error when using standard ACID function
• LSD function can now handle larger wavelength ranges, includes error if this will result in an increase in computation time

What's Changed

• tutorials fixed, calculate deltav function added + doc updates by @ldolan05 in #17

Full Changelog: v0.1.0...v0.1.1