v1.4.0

Includes a number of updates and important bug fixes:

• New option to only use a random subset of genes for generating a core alignment thanks to @mgalardini
• New option to only consider valid genes (without stop premature codons and of correct length). Thanks to issue #263 raised by @NickJD
• Important fix to the panaroo-merge-graph script which had a bug that prevented the --merge-paralogs options from working. This is now the recommended way to run this script.
• Fixed bug in panaroo-integrate raised by @maxibor
• added warning if no matching sequences are found between the annotations and the corresponding fasta file/section
• added check for the number of core genes to prevent a crash if no clusters passed the core frequency threshold